1
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Catanzaro A, Genco A, Louca C, Ruiz-Tijerina DA, Gillard DJ, Sortino L, Kozikov A, Alexeev EM, Pisoni R, Hague L, Watanabe K, Taniguchi T, Ensslin K, Novoselov KS, Fal'ko V, Tartakovskii AI. Resonant Band Hybridization in Alloyed Transition Metal Dichalcogenide Heterobilayers. Adv Mater 2024; 36:e2309644. [PMID: 38279553 DOI: 10.1002/adma.202309644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/20/2023] [Indexed: 01/28/2024]
Abstract
Bandstructure engineering using alloying is widely utilized for achieving optimized performance in modern semiconductor devices. While alloying has been studied in monolayer transition metal dichalcogenides, its application in van der Waals heterostructures built from atomically thin layers is largely unexplored. Here, heterobilayers made from monolayers of WSe2 (or MoSe2) and MoxW1 - xSe2 alloy are fabricated and nontrivial tuning of the resultant bandstructure is observed as a function of concentration x. This evolution is monitored by measuring the energy of photoluminescence (PL) of the interlayer exciton (IX) composed of an electron and hole residing in different monolayers. In MoxW1 - xSe2/WSe2, a strong IX energy shift of ≈100 meV is observed for x varied from 1 to 0.6. However, for x < 0.6 this shift saturates and the IX PL energy asymptotically approaches that of the indirect bandgap in bilayer WSe2. This observation is theoretically interpreted as the strong variation of the conduction band K valley for x > 0.6, with IX PL arising from the K - K transition, while for x < 0.6, the bandstructure hybridization becomes prevalent leading to the dominating momentum-indirect K - Q transition. This bandstructure hybridization is accompanied with strong modification of IX PL dynamics and nonlinear exciton properties. This work provides foundation for bandstructure engineering in van der Waals heterostructures highlighting the importance of hybridization effects and opening a way to devices with accurately tailored electronic properties.
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Affiliation(s)
- Alessandro Catanzaro
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - Armando Genco
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, Milano, 20133, Italy
| | - Charalambos Louca
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci, 32, Milano, 20133, Italy
| | - David A Ruiz-Tijerina
- Departamento de Física Química, Instituto de Física, Universidad Nacional Autónoma de México, Ciudad de México, C.P., 04510, Mexico, México
| | - Daniel J Gillard
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
| | - Luca Sortino
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Chair in Hybrid Nanosystems, Nanoinstitute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, 80539, Munich, Germany
| | - Aleksey Kozikov
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Evgeny M Alexeev
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, S3 7RH, UK
- Cambridge Graphene Centre, University of Cambridge, 9 J. J. Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zurich, Zurich, CH-8093, Switzerland
| | - Lee Hague
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, Zurich, CH-8093, Switzerland
| | - Kostya S Novoselov
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, 117546, Singapore
| | - Vladimir Fal'ko
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- Henry Royce Institute for Advanced Materials, University of Manchester, Manchester, M13 9PL, United Kingdom
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2
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de Vries F, Slizovskiy S, Tomić P, Krishna Kumar R, Garcia-Ruiz A, Zheng G, Portolés E, Ponomarenko LA, Geim AK, Watanabe K, Taniguchi T, Fal’ko V, Ensslin K, Ihn T, Rickhaus P. Kagome Quantum Oscillations in Graphene Superlattices. Nano Lett 2024; 24:601-606. [PMID: 38180909 PMCID: PMC10797620 DOI: 10.1021/acs.nanolett.3c03524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 12/17/2023] [Accepted: 12/19/2023] [Indexed: 01/07/2024]
Abstract
Electronic spectra of solids subjected to a magnetic field are often discussed in terms of Landau levels and Hofstadter-butterfly-style Brown-Zak minibands manifested by magneto-oscillations in two-dimensional electron systems. Here, we present the semiclassical precursors of these quantum magneto-oscillations which appear in graphene superlattices at low magnetic field near the Lifshitz transitions and persist at elevated temperatures. These oscillations originate from Aharonov-Bohm interference of electron waves following open trajectories that belong to a kagome-shaped network of paths characteristic for Lifshitz transitions in the moire superlattice minibands of twistronic graphenes.
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Affiliation(s)
| | - Sergey Slizovskiy
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - Petar Tomić
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Roshan Krishna Kumar
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, Barcelona 08028, Spain
| | - Aitor Garcia-Ruiz
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - Giulia Zheng
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Elías Portolés
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | | | - Andre K. Geim
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - Kenji Watanabe
- National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Vladimir Fal’ko
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
- Henry
Royce
Institute for Advanced Materials, Manchester M13 9PL, United Kingdom
| | - Klaus Ensslin
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Thomas Ihn
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Peter Rickhaus
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
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3
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Iwakiri S, Mestre-Torà A, Portolés E, Visscher M, Perego M, Zheng G, Taniguchi T, Watanabe K, Sigrist M, Ihn T, Ensslin K. Tunable quantum interferometer for correlated moiré electrons. Nat Commun 2024; 15:390. [PMID: 38195747 PMCID: PMC10776667 DOI: 10.1038/s41467-023-44671-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 12/20/2023] [Indexed: 01/11/2024] Open
Abstract
Magic-angle twisted bilayer graphene can host a variety of gate-tunable correlated states - including superconducting and correlated insulator states. Recently, junction-based superconducting moiré devices have been introduced, enabling the study of the charge, spin and orbital nature of superconductivity, as well as the coherence of moiré electrons in magic-angle twisted bilayer graphene. Complementary fundamental coherence effects-in particular, the Little-Parks effect in a superconducting ring and the Aharonov-Bohm effect in a normally conducting ring - have not yet been reported in moiré devices. Here, we observe both phenomena in a single gate-defined ring device, where we can embed a superconducting or normally conducting ring in a correlated or band insulator. The Little-Parks effect is seen in the superconducting phase diagram as a function of density and magnetic field, confirming the effective charge of 2e. We also find that the coherence length of conducting moiré electrons exceeds several microns at 50 mK. In addition, we identify a regime characterized by h/e-periodic oscillations but with superconductor-like nonlinear transport.
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Affiliation(s)
- Shuichi Iwakiri
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland.
| | | | - Elías Portolés
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Marieke Visscher
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Marta Perego
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Giulia Zheng
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Manfred Sigrist
- Institute for Theoretical Physics, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Thomas Ihn
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Klaus Ensslin
- Laboratory for Solid State Physics, ETH Zurich, CH-8093, Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093, Zurich, Switzerland
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4
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Portolés E, Iwakiri S, Zheng G, Rickhaus P, Taniguchi T, Watanabe K, Ihn T, Ensslin K, de Vries FK. A tunable monolithic SQUID in twisted bilayer graphene. Nat Nanotechnol 2022; 17:1159-1164. [PMID: 36280761 DOI: 10.1038/s41565-022-01222-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 09/05/2022] [Indexed: 06/16/2023]
Abstract
Magic-angle twisted bilayer graphene (MATBG) hosts a number of correlated states of matter that can be tuned by electrostatic doping1-4. Transport5,6 and scanning-probe7-9 experiments have shown evidence for band, correlated and Chern insulators along with superconductivity. This variety of in situ tunable states has allowed for the realization of tunable Josephson junctions10-12. However, although phase-coherent phenomena have been measured10-12, no control of the phase difference of the superconducting condensates has been demonstrated so far. Here we build on previous gate-defined junction realizations and form a superconducting quantum interference device13 (SQUID) in MATBG, where the superconducting phase difference is controlled through the magnetic field. We observe magneto-oscillations of the critical current, demonstrating long-range coherence of superconducting charge carriers with an effective charge of 2e. We tune to both asymmetric and symmetric SQUID configurations by electrostatically controlling the critical currents through the junctions. This tunability allows us to study the inductances in the device, finding values of up to 2 μH. Furthermore, we directly probe the current-phase relation of one of the junctions of the device. Our results show that complex devices in MATBG can be realized and used to reveal the properties of the material. We envision our findings, together with the established history of applications SQUIDs have14-16, will foster the development of a wide range of devices such as phase-slip junctions17 or high kinetic inductance detectors18.
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Affiliation(s)
- Elías Portolés
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland.
| | - Shuichi Iwakiri
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
- Quantum Center, ETH Zurich, Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland.
- Quantum Center, ETH Zurich, Zurich, Switzerland.
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5
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Iwakiri S, de Vries FK, Portolés E, Zheng G, Taniguchi T, Watanabe K, Ihn T, Ensslin K. Gate-Defined Electron Interferometer in Bilayer Graphene. Nano Lett 2022; 22:6292-6297. [PMID: 35880910 DOI: 10.1021/acs.nanolett.2c01874] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We present an electron interferometer defined purely by electrostatic gating in an encapsulated bilayer graphene. This minimizes possible sample degradation introduced by conventional etching methods when preparing quantum devices. The device quality is demonstrated by observing Aharonov-Bohm (AB) oscillations with a period of h/e, h/2e, h/3e, and h/4e, witnessing a coherence length of many microns. The AB oscillations as well as the type of carriers (electrons or holes) are seamlessly tunable with gating. The coherence length longer than the ring perimeter and semiclassical trajectory of the carrier are established from the analysis of the temperature and magnetic field dependence of the oscillations. Our gate-defined ring geometry has the potential to evolve into a platform for exploring correlated quantum states such as superconductivity in interferometers in twisted bilayer graphene.
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Affiliation(s)
- Shuichi Iwakiri
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Elías Portolés
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
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6
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Ramanandan S, Tomić P, Morgan NP, Giunto A, Rudra A, Ensslin K, Ihn T, Fontcuberta i Morral A. Coherent Hole Transport in Selective Area Grown Ge Nanowire Networks. Nano Lett 2022; 22:4269-4275. [PMID: 35507698 PMCID: PMC9136922 DOI: 10.1021/acs.nanolett.2c00358] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 04/23/2022] [Indexed: 05/28/2023]
Abstract
Holes in germanium nanowires have emerged as a realistic platform for quantum computing based on spin qubit logic. On top of the large spin-orbit coupling that allows fast qubit operation, nanowire geometry and orientation can be tuned to cancel out charge noise and hyperfine interaction. Here, we demonstrate a scalable approach to synthesize and organize Ge nanowires on silicon (100)-oriented substrates. Germanium nanowire networks are obtained by selectively growing on nanopatterned slits in a metalorganic vapor phase epitaxy system. Low-temperature electronic transport measurements are performed on nanowire Hall bar devices revealing high hole doping of ∼1018 cm-3 and mean free path of ∼10 nm. Quantum diffusive transport phenomena, universal conductance fluctuations, and weak antilocalization are revealed through magneto transport measurements yielding a coherence and a spin-orbit length of the order of 100 and 10 nm, respectively.
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Affiliation(s)
- Santhanu
Panikar Ramanandan
- Laboratory
of Semiconductor Materials, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne 1015, Switzerland
| | - Petar Tomić
- Solid
State Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - Nicholas Paul Morgan
- Laboratory
of Semiconductor Materials, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne 1015, Switzerland
| | - Andrea Giunto
- Laboratory
of Semiconductor Materials, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne 1015, Switzerland
| | - Alok Rudra
- Laboratory
of Semiconductor Materials, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne 1015, Switzerland
| | - Klaus Ensslin
- Solid
State Laboratory, ETH Zurich, 8093 Zurich, Switzerland
- Quantum
Center, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Thomas Ihn
- Solid
State Laboratory, ETH Zurich, 8093 Zurich, Switzerland
- Quantum
Center, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Anna Fontcuberta i Morral
- Laboratory
of Semiconductor Materials, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne EPFL, Lausanne 1015, Switzerland
- Institute
of Physics, Faculty of Basic Sciences, Ecole
Polytechnique Fédérale de Lausanne EPFL, Lausanne 1015, Switzerland
- Center
for Quantum Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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7
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Tong C, Kurzmann A, Garreis R, Huang WW, Jele S, Eich M, Ginzburg L, Mittag C, Watanabe K, Taniguchi T, Ensslin K, Ihn T. Pauli Blockade of Tunable Two-Electron Spin and Valley States in Graphene Quantum Dots. Phys Rev Lett 2022; 128:067702. [PMID: 35213193 DOI: 10.1103/physrevlett.128.067702] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 11/23/2021] [Accepted: 01/10/2022] [Indexed: 05/21/2023]
Abstract
Pauli blockade mechanisms-whereby carrier transport through quantum dots (QD) is blocked due to selection rules even when energetically allowed-are a direct manifestation of the Pauli exclusion principle, as well as a key mechanism for manipulating and reading out spin qubits. The Pauli spin blockade is well established for systems such as GaAs QDs, but is to be further explored for systems with additional degrees of freedom, such as the valley quantum numbers in carbon-based materials or silicon. Here we report experiments on coupled bilayer graphene double quantum dots, in which the spin and valley states are precisely controlled, enabling the observation of the two-electron combined blockade physics. We demonstrate that the doubly occupied single dot switches between two different ground states with gate and magnetic-field tuning, allowing for the switching of selection rules: with a spin-triplet-valley-singlet ground state, valley blockade is observed; and with the spin-singlet-valley-triplet ground state, robust spin blockade is shown.
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Affiliation(s)
- Chuyao Tong
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Rebekka Garreis
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Wei Wister Huang
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Samuel Jele
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Lev Ginzburg
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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8
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Tomić P, Rickhaus P, Garcia-Ruiz A, Zheng G, Portolés E, Fal'ko V, Watanabe K, Taniguchi T, Ensslin K, Ihn T, de Vries FK. Scattering between Minivalleys in Twisted Double Bilayer Graphene. Phys Rev Lett 2022; 128:057702. [PMID: 35179933 DOI: 10.1103/physrevlett.128.057702] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 11/29/2021] [Accepted: 12/08/2021] [Indexed: 06/14/2023]
Abstract
A unique feature of the complex band structures of moiré materials is the presence of minivalleys, their hybridization, and scattering between them. Here, we investigate magnetotransport oscillations caused by scattering between minivalleys-a phenomenon analogous to magnetointersubband oscillations-in a twisted double bilayer graphene sample with a twist angle of 1.94°. We study and discuss the potential scattering mechanisms and find an electron-phonon mechanism and valley conserving scattering to be likely. Finally, we discuss the relevance of our findings for different materials and twist angles.
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Affiliation(s)
- Petar Tomić
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Peter Rickhaus
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Aitor Garcia-Ruiz
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Giulia Zheng
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Elías Portolés
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Vladimir Fal'ko
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Henry Royce Institute for Advanced Materials, M13 9PL Manchester, United Kingdom
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Klaus Ensslin
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum Center, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum Center, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Folkert K de Vries
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
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9
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Nicolí G, Adam C, Röösli MP, Märki P, Scharnetzky J, Reichl C, Wegscheider W, Ihn TM, Ensslin K. Spin-Selective Equilibration among Integer Quantum Hall Edge Channels. Phys Rev Lett 2022; 128:056802. [PMID: 35179909 DOI: 10.1103/physrevlett.128.056802] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 01/03/2022] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
The equilibration between quantum Hall edge modes is known to depend on the disorder potential and the steepness of the edge. Modern samples with higher mobilities and setups with lower electron temperatures call for a further exploration of the topic. We develop a framework to systematically measure and analyze the equilibration of many (up to 8) integer edge modes. Our results show that spin-selective coupling dominates even for non-neighboring channels with parallel spin. Changes in magnetic field and bulk density let us control the equilibration until it is almost completely suppressed and dominated only by individual microscopic scatterers. This method could serve as a guideline to investigate and design improved devices, and to study fractional and other exotic states.
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Affiliation(s)
- Giorgio Nicolí
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Christoph Adam
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Marc P Röösli
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Peter Märki
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Jan Scharnetzky
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Christian Reichl
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Thomas M Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
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10
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Kurzmann A, Kleeorin Y, Tong C, Garreis R, Knothe A, Eich M, Mittag C, Gold C, de Vries FK, Watanabe K, Taniguchi T, Fal'ko V, Meir Y, Ihn T, Ensslin K. Kondo effect and spin-orbit coupling in graphene quantum dots. Nat Commun 2021; 12:6004. [PMID: 34650056 PMCID: PMC8516925 DOI: 10.1038/s41467-021-26149-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 09/17/2021] [Indexed: 11/30/2022] Open
Abstract
The Kondo effect is a cornerstone in the study of strongly correlated fermions. The coherent exchange coupling of conduction electrons to local magnetic moments gives rise to a Kondo cloud that screens the impurity spin. Here we report on the interplay between spin-orbit interaction and the Kondo effect, that can lead to a underscreened Kondo effects in quantum dots in bilayer graphene. More generally, we introduce a different experimental platform for studying Kondo physics. In contrast to carbon nanotubes, where nanotube chirality determines spin-orbit coupling breaking the SU(4) symmetry of the electronic states relevant for the Kondo effect, we study a planar carbon material where a small spin-orbit coupling of nominally flat graphene is enhanced by zero-point out-of-plane phonons. The resulting two-electron triplet ground state in bilayer graphene dots provides a route to exploring the Kondo effect with a small spin-orbit interaction.
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Affiliation(s)
- Annika Kurzmann
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland.
| | - Yaakov Kleeorin
- Center for the Physics of Evolving Systems, Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Chuyao Tong
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
| | - Rebekka Garreis
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
| | - Angelika Knothe
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
| | - Christopher Mittag
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
| | - Carolin Gold
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
| | | | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, 305-0044, Japan
| | - Vladimir Fal'ko
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - Yigal Meir
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
- Quantum Center, ETH Zurich, Zurich, 8093, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, Zürich, CH-8093, Switzerland
- Quantum Center, ETH Zurich, Zurich, 8093, Switzerland
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11
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Rickhaus P, de Vries FK, Zhu J, Portoles E, Zheng G, Masseroni M, Kurzmann A, Taniguchi T, Watanabe K, MacDonald AH, Ihn T, Ensslin K. Correlated electron-hole state in twisted double-bilayer graphene. Science 2021; 373:1257-1260. [PMID: 34516786 DOI: 10.1126/science.abc3534] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | | | - Jihang Zhu
- Department of Physics, University of Texas at Austin, Austin, TX 78712, USA
| | - Elías Portoles
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Michele Masseroni
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Allan H MacDonald
- Department of Physics, University of Texas at Austin, Austin, TX 78712, USA
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland.,Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland.,Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
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12
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Gold C, Knothe A, Kurzmann A, Garcia-Ruiz A, Watanabe K, Taniguchi T, Fal'ko V, Ensslin K, Ihn T. Coherent Jetting from a Gate-Defined Channel in Bilayer Graphene. Phys Rev Lett 2021; 127:046801. [PMID: 34355933 DOI: 10.1103/physrevlett.127.046801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 05/18/2021] [Indexed: 06/13/2023]
Abstract
Graphene has evolved as a platform for quantum transport that can compete with the best and cleanest semiconductor systems. Here, we report on the observation of distinct electronic jets emanating from a narrow split-gate-defined channel in bilayer graphene. We find that these jets, which are visible via their interference patterns, occur predominantly with an angle of 60° between each other. This observation is related to the trigonal warping in the band structure of bilayer graphene, which, in conjunction with electron injection through a constriction, leads to a valley-dependent selection of momenta. This experimental observation of electron jetting has consequences for carrier transport in two-dimensional materials with a trigonally warped band structure in general, as well as for devices relying on ballistic and valley-selective transport.
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Affiliation(s)
- Carolin Gold
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Angelika Knothe
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Annika Kurzmann
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Aitor Garcia-Ruiz
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Vladimir Fal'ko
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department of Physics, University of Manchester, Manchester M13 9PL, United Kingdom
- Henry Royce Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
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13
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de Vries FK, Portolés E, Zheng G, Taniguchi T, Watanabe K, Ihn T, Ensslin K, Rickhaus P. Gate-defined Josephson junctions in magic-angle twisted bilayer graphene. Nat Nanotechnol 2021; 16:760-763. [PMID: 33941917 DOI: 10.1038/s41565-021-00896-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/10/2021] [Indexed: 05/12/2023]
Abstract
In situ electrostatic control of two-dimensional superconductivity1 is commonly limited due to large charge carrier densities, and gate-defined Josephson junctions are therefore rare2,3. Magic-angle twisted bilayer graphene (MATBG)4-8 has recently emerged as a versatile platform that combines metallic, superconducting, magnetic and insulating phases in a single crystal9-14. Although MATBG appears to be an ideal two-dimensional platform for gate-tunable superconductivity9,11,13, progress towards practical implementations has been hindered by the need for well-defined gated regions. Here we use multilayer gate technology to create a device based on two distinct phases in adjustable regions of MATBG. We electrostatically define the superconducting and insulating regions of a Josephson junction and observe tunable d.c. and a.c. Josephson effects15,16. The ability to tune the superconducting state within a single material circumvents interface and fabrication challenges, which are common in multimaterial nanostructures. This work is an initial step towards devices where gate-defined correlated states are connected in single-crystal nanostructures. We envision applications in superconducting electronics17,18 and quantum information technology19,20.
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Affiliation(s)
| | - Elías Portolés
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland.
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14
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Röösli MP, Hug M, Nicolí G, Märki P, Reichl C, Rosenow B, Wegscheider W, Ensslin K, Ihn T. Fractional Coulomb blockade for quasi-particle tunneling between edge channels. Sci Adv 2021; 7:eabf5547. [PMID: 33962947 PMCID: PMC8104872 DOI: 10.1126/sciadv.abf5547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 03/10/2021] [Indexed: 06/12/2023]
Abstract
In the fractional quantum Hall effect, the elementary excitations are quasi-particles with fractional charges as predicted by theory and demonstrated by noise and interference experiments. We observe Coulomb blockade of fractional charges in the measured magneto-conductance of a 1.4-micron-wide quantum dot. Interaction-driven edge reconstruction separates the dot into concentric compressible regions with fractionally charged excitations and incompressible regions acting as tunnel barriers for quasi-particles. Our data show the formation of incompressible regions of filling factors 2/3 and 1/3. Comparing data at fractional filling factors to filling factor 2, we extract the fractional quasi-particle charge e */e = 0.32 ± 0.03 and 0.35 ± 0.05. Our investigations extend and complement quantum Hall Fabry-Pérot interference experiments investigating the nature of anyonic fractional quasi-particles.
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Affiliation(s)
- Marc P Röösli
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland.
| | - Michael Hug
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Giorgio Nicolí
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Peter Märki
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Christian Reichl
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Bernd Rosenow
- Institute for Theoretical Physics, Leipzig University Leipzig D-04009, Germany
| | - Werner Wegscheider
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
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15
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Garreis R, Knothe A, Tong C, Eich M, Gold C, Watanabe K, Taniguchi T, Fal'ko V, Ihn T, Ensslin K, Kurzmann A. Shell Filling and Trigonal Warping in Graphene Quantum Dots. Phys Rev Lett 2021; 126:147703. [PMID: 33891439 DOI: 10.1103/physrevlett.126.147703] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 03/11/2021] [Indexed: 06/12/2023]
Abstract
Transport measurements through a few-electron circular quantum dot in bilayer graphene display bunching of the conductance resonances in groups of four, eight, and twelve. This is in accordance with the spin and valley degeneracies in bilayer graphene and an additional threefold "minivalley degeneracy" caused by trigonal warping. For small electron numbers, implying a small dot size and a small displacement field, a two-dimensional s shell and then a p shell are successively filled with four and eight electrons, respectively. For electron numbers larger than 12, as the dot size and the displacement field increase, the single-particle ground state evolves into a threefold degenerate minivalley ground state. A transition between these regimes is observed in our measurements and can be described by band-structure calculations. Measurements in the magnetic field confirm Hund's second rule for spin filling of the quantum dot levels, emphasizing the importance of exchange interaction effects.
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Affiliation(s)
- R Garreis
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
| | - A Knothe
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - C Tong
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
| | - M Eich
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
| | - C Gold
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
| | - K Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - V Fal'ko
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Henry Royce Institute for Advanced Materials, M13 9PL, Manchester, United Kingdom
| | - T Ihn
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
| | - K Ensslin
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
| | - A Kurzmann
- ETH Zurich (Swiss Federal Institute of Technology in Zurich), 8093 Zurich, Switzerland
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16
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Tong C, Garreis R, Knothe A, Eich M, Sacchi A, Watanabe K, Taniguchi T, Fal'ko V, Ihn T, Ensslin K, Kurzmann A. Tunable Valley Splitting and Bipolar Operation in Graphene Quantum Dots. Nano Lett 2021; 21:1068-1073. [PMID: 33449702 DOI: 10.1021/acs.nanolett.0c04343] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Quantum states in graphene are 2-fold degenerate in spins, and 2-fold in valleys. Both degrees of freedom can be utilized for qubit preparations. In our bilayer graphene quantum dots, we demonstrate that the valley g-factor gv, defined analogously to the spin g-factor gs for valley splitting in a perpendicular magnetic field, is tunable by over a factor of 4 from 20 to 90, by gate voltage adjustments only. Larger gv results from larger electronic dot sizes, determined from the charging energy. On our versatile device, bipolar operation, charging our quantum dot with charge carriers of the same or the opposite polarity as the leads, can be performed. Dots of both polarities are tunable to the first charge carrier, such that the transition from an electron to a hole dot by the action of the plunger gate can be observed. Addition of gates easily extends the system to host tunable double dots.
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Affiliation(s)
- Chuyao Tong
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Rebekka Garreis
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Angelika Knothe
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Agnese Sacchi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Vladimir Fal'ko
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Henry Royce Institute for Advanced Materials, M13 9PL, Manchester, U.K
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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17
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de Vries FK, Zhu J, Portolés E, Zheng G, Masseroni M, Kurzmann A, Taniguchi T, Watanabe K, MacDonald AH, Ensslin K, Ihn T, Rickhaus P. Combined Minivalley and Layer Control in Twisted Double Bilayer Graphene. Phys Rev Lett 2020; 125:176801. [PMID: 33156662 DOI: 10.1103/physrevlett.125.176801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
Control over minivalley polarization and interlayer coupling is demonstrated in double bilayer graphene twisted with an angle of 2.37°. This intermediate angle is small enough for the minibands to form and large enough such that the charge carrier gases in the layers can be tuned independently. Using a dual-gated geometry we identify and control all possible combinations of minivalley polarization via the population of the two bilayers. An applied displacement field opens a band gap in either of the two bilayers, allowing us to even obtain full minivalley polarization. In addition, the carriers, formerly separated by their minivalley character, are mixed by tuning through a Lifshitz transition, where the Fermi surface topology changes. The high degree of control over the minivalley character of the bulk charge transport in twisted double bilayer graphene offers new opportunities for realizing valleytronics devices such as valley valves, filters, and logic gates.
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Affiliation(s)
- Folkert K de Vries
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Jihang Zhu
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Elías Portolés
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Giulia Zheng
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Michele Masseroni
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Annika Kurzmann
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Allan H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Klaus Ensslin
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Peter Rickhaus
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
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18
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Bartošík M, Mach J, Piastek J, Nezval D, Konečný M, Švarc V, Ensslin K, Šikola T. Mechanism and Suppression of Physisorbed-Water-Caused Hysteresis in Graphene FET Sensors. ACS Sens 2020; 5:2940-2949. [PMID: 32872770 DOI: 10.1021/acssensors.0c01441] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hysteresis is a problem in field-effect transistors (FETs) often caused by defects and charge traps inside a gate isolating (e.g., SiO2) layer. This work shows that graphene-based FETs also exhibit hysteresis due to water physisorbed on top of graphene determined by the relative humidity level, which naturally happens in biosensors and ambient operating sensors. The hysteresis effect is explained by trapping of electrons by physisorbed water, and it is shown that this hysteresis can be suppressed using short pulses of alternating gate voltages.
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Affiliation(s)
- Miroslav Bartošík
- Central European Institute of Technology - Brno University of Technology (CEITEC BUT), Purkyňova 123, 612 00 Brno, Czech Republic
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
- Department of Physics and Materials Engineering, Faculty of Technology, Tomas Bata University in Zlín, Vavrečkova 275, 760 01 Zlín, Czech Republic
| | - Jindřich Mach
- Central European Institute of Technology - Brno University of Technology (CEITEC BUT), Purkyňova 123, 612 00 Brno, Czech Republic
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
| | - Jakub Piastek
- Central European Institute of Technology - Brno University of Technology (CEITEC BUT), Purkyňova 123, 612 00 Brno, Czech Republic
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
| | - David Nezval
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
| | - Martin Konečný
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
| | - Vojtěch Švarc
- Central European Institute of Technology - Brno University of Technology (CEITEC BUT), Purkyňova 123, 612 00 Brno, Czech Republic
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, CH 8093 Zürich, Switzerland
| | - Tomáš Šikola
- Central European Institute of Technology - Brno University of Technology (CEITEC BUT), Purkyňova 123, 612 00 Brno, Czech Republic
- Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic
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19
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Lee Y, Knothe A, Overweg H, Eich M, Gold C, Kurzmann A, Klasovika V, Taniguchi T, Wantanabe K, Fal'ko V, Ihn T, Ensslin K, Rickhaus P. Tunable Valley Splitting due to Topological Orbital Magnetic Moment in Bilayer Graphene Quantum Point Contacts. Phys Rev Lett 2020; 124:126802. [PMID: 32281833 DOI: 10.1103/physrevlett.124.126802] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 02/28/2020] [Indexed: 05/21/2023]
Abstract
In multivalley semiconductors, the valley degree of freedom can be potentially used to store, manipulate, and read quantum information, but its control remains challenging. The valleys in bilayer graphene can be addressed by a perpendicular magnetic field which couples by the valley g factor g_{v}. However, control over g_{v} has not been demonstrated yet. We experimentally determine the energy spectrum of a quantum point contact realized by a suitable gate geometry in bilayer graphene. Using finite bias spectroscopy, we measure the energy scales arising from the lateral confinement as well as the Zeeman splitting and find a spin g factor g_{s}∼2. g_{v} can be tuned by a factor of 3 using vertical electric fields, g_{v}∼40-120. The results are quantitatively explained by a calculation considering topological magnetic moment and its dependence on confinement and the vertical displacement field.
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Affiliation(s)
- Yongjin Lee
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Angelika Knothe
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Hiske Overweg
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Marius Eich
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Carolin Gold
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Annika Kurzmann
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Veronika Klasovika
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Wantanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Vladimir Fal'ko
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Thomas Ihn
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Klaus Ensslin
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
| | - Peter Rickhaus
- Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland
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20
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Rickhaus P, Liu MH, Kurpas M, Kurzmann A, Lee Y, Overweg H, Eich M, Pisoni R, Taniguchi T, Watanabe K, Richter K, Ensslin K, Ihn T. The electronic thickness of graphene. Sci Adv 2020; 6:eaay8409. [PMID: 32201727 PMCID: PMC7069711 DOI: 10.1126/sciadv.aay8409] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/16/2019] [Indexed: 05/31/2023]
Abstract
When two dimensional crystals are atomically close, their finite thickness becomes relevant. Using transport measurements, we investigate the electrostatics of two graphene layers, twisted by θ = 22° such that the layers are decoupled by the huge momentum mismatch between the K and K' points of the two layers. We observe a splitting of the zero-density lines of the two layers with increasing interlayer energy difference. This splitting is given by the ratio of single-layer quantum capacitance over interlayer capacitance C m and is therefore suited to extract C m. We explain the large observed value of C m by considering the finite dielectric thickness d g of each graphene layer and determine d g ≈ 2.6 Å. In a second experiment, we map out the entire density range with a Fabry-Pérot resonator. We can precisely measure the Fermi wavelength λ in each layer, showing that the layers are decoupled. Our findings are reproduced using tight-binding calculations.
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Affiliation(s)
- Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Ming-Hao Liu
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - Marcin Kurpas
- Institute of Physics, University of Silesia in Katowice, 41-500 Chorzów, Poland
| | - Annika Kurzmann
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
- Microsoft Research Cambridge, Cambridge, UK
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Klaus Richter
- Institute of Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
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21
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Safeer CK, Ontoso N, Ingla-Aynés J, Herling F, Pham VT, Kurzmann A, Ensslin K, Chuvilin A, Robredo I, Vergniory MG, de Juan F, Hueso LE, Calvo MR, Casanova F. Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe 2 at Room Temperature. Nano Lett 2019; 19:8758-8766. [PMID: 31661967 DOI: 10.1021/acs.nanolett.9b03485] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Efficient and versatile spin-to-charge current conversion is crucial for the development of spintronic applications, which strongly rely on the ability to electrically generate and detect spin currents. In this context, the spin Hall effect has been widely studied in heavy metals with strong spin-orbit coupling. While the high crystal symmetry in these materials limits the conversion to the orthogonal configuration, unusual configurations are expected in low-symmetry transition-metal dichalcogenide semimetals, which could add flexibility to the electrical injection and detection of pure spin currents. Here, we report the observation of spin-to-charge conversion in MoTe2 flakes, which are stacked in graphene lateral spin valves. We detect two distinct contributions arising from the conversion of two different spin orientations. In addition to the conventional conversion where the spin polarization is orthogonal to the charge current, we also detect a conversion where the spin polarization and the charge current are parallel. Both contributions, which could arise either from bulk spin Hall effect or surface Edelstein effect, show large efficiencies comparable to the best spin Hall metals and topological insulators. Our finding enables the simultaneous conversion of spin currents with any in-plane spin polarization in one single experimental configuration.
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Affiliation(s)
- C K Safeer
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Nerea Ontoso
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Josep Ingla-Aynés
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Franz Herling
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Van Tuong Pham
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Annika Kurzmann
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Andrey Chuvilin
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE, Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
| | - Iñigo Robredo
- Donostia International Physics Center (DIPC) , 20018 Donostia-San Sebastian , Basque Country , Spain
- Department of Condensed Matter Physics , University of the Basque Country (UPV/EHU) , 48080 Bilbao , Basque Country , Spain
| | - Maia G Vergniory
- IKERBASQUE, Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
- Donostia International Physics Center (DIPC) , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Fernando de Juan
- IKERBASQUE, Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
- Donostia International Physics Center (DIPC) , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Luis E Hueso
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE, Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
| | - M Reyes Calvo
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE, Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
- Departamento de Física Aplicada , Universidad de Alicante , 03690 Alicante , Spain
| | - Fèlix Casanova
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE, Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
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22
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Rickhaus P, Zheng G, Lado JL, Lee Y, Kurzmann A, Eich M, Pisoni R, Tong C, Garreis R, Gold C, Masseroni M, Taniguchi T, Wantanabe K, Ihn T, Ensslin K. Gap Opening in Twisted Double Bilayer Graphene by Crystal Fields. Nano Lett 2019; 19:8821-8828. [PMID: 31670969 DOI: 10.1021/acs.nanolett.9b03660] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Crystal fields occur due to a potential difference between chemically different atomic species. In van der Waals heterostructures such fields are naturally present perpendicular to the planes. It has been realized recently that twisted graphene multilayers provide powerful playgrounds to engineer electronic properties by the number of layers, the twist angle, applied electric biases, electronic interactions, and elastic relaxations, but crystal fields have not received the attention they deserve. Here, we show that the band structure of large-angle twisted double bilayer graphene is strongly modified by crystal fields. In particular, we experimentally demonstrate that twisted double bilayer graphene, encapsulated between hBN layers, exhibits an intrinsic band gap. By the application of an external field, the gaps in the individual bilayers can be closed, allowing to determine the crystal fields. We find that crystal fields point from the outer to the inner layers with strengths in the bottom/top bilayer [Formula: see text] = 0.13 V/nm ≈ [Formula: see text] = 0.12 V/nm. We show both by means of first-principles calculations and low energy models that crystal fields open a band gap in the ground state. Our results put forward a physical scenario in which a crystal field effect in carbon substantially impacts the low energy properties of twisted double bilayer graphene, suggesting that such contributions must be taken into account in other regimes to faithfully predict the electronic properties of twisted graphene multilayers.
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Affiliation(s)
- Peter Rickhaus
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Jose L Lado
- Department of Applied Physics , Aalto University , Espoo , Finland
- Institute for Theoretical Physics , ETH Zurich , 8093 Zurich , Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Marius Eich
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Chuyao Tong
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Rebekka Garreis
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Carolin Gold
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Michele Masseroni
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Takashi Taniguchi
- National Institute for Material Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Kenji Wantanabe
- National Institute for Material Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Thomas Ihn
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
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23
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Ensslin K. Electrons in graphene go with the flow. Nature 2019; 576:45-46. [DOI: 10.1038/d41586-019-03702-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Nicolí G, Märki P, Bräm BA, Röösli MP, Hennel S, Hofmann A, Reichl C, Wegscheider W, Ihn T, Ensslin K. Quantum dot thermometry at ultra-low temperature in a dilution refrigerator with a 4He immersion cell. Rev Sci Instrum 2019; 90:113901. [PMID: 31779415 DOI: 10.1063/1.5127830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 10/26/2019] [Indexed: 06/10/2023]
Abstract
Experiments performed at a temperature of a few millikelvins require effective thermalization schemes, low-pass filtering of the measurement lines, and low-noise electronics. Here, we report on the modifications to a commercial dilution refrigerator with a base temperature of 3.5 mK that enable us to lower the electron temperature to 6.7 mK measured from the Coulomb peak width of a quantum dot gate-defined in an [Al]GaAs heteostructure. We present the design and implementation of a liquid 4He immersion cell tight against superleaks, implement an innovative wiring technology, and develop optimized transport measurement procedures.
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Affiliation(s)
- G Nicolí
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - P Märki
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - B A Bräm
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - M P Röösli
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - S Hennel
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - A Hofmann
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland
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25
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Pisoni R, Davatz T, Watanabe K, Taniguchi T, Ihn T, Ensslin K. Absence of Interlayer Tunnel Coupling of K-Valley Electrons in Bilayer MoS_{2}. Phys Rev Lett 2019; 123:117702. [PMID: 31573263 DOI: 10.1103/physrevlett.123.117702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Indexed: 06/10/2023]
Abstract
In Bernal stacked bilayer graphene interlayer coupling significantly affects the electronic band structure compared to monolayer graphene. Here we present magnetotransport experiments on high-quality n-doped bilayer MoS_{2}. By measuring the evolution of the Landau levels as a function of electron density and applied magnetic field we are able to investigate the occupation of conduction band states, the interlayer coupling in pristine bilayer MoS_{2}, and how these effects are governed by electron-electron interactions. We find that the two layers of the bilayer MoS_{2} behave as two independent electronic systems where a twofold Landau level's degeneracy is observed for each MoS_{2} layer. At the onset of the population of the bottom MoS_{2} layer we observe a large negative compressibility caused by the exchange interaction. These observations, enabled by the high electronic quality of our samples, demonstrate weak interlayer tunnel coupling but strong interlayer electrostatic coupling in pristine bilayer MoS_{2}. The conclusions from the experiments may be relevant also to other transition metal dichalcogenide materials.
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Affiliation(s)
- Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Tim Davatz
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
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26
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Krähenmann T, Fischer SG, Röösli M, Ihn T, Reichl C, Wegscheider W, Ensslin K, Gefen Y, Meir Y. Auger-spectroscopy in quantum Hall edge channels and the missing energy problem. Nat Commun 2019; 10:3915. [PMID: 31477720 PMCID: PMC6718669 DOI: 10.1038/s41467-019-11888-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 08/05/2019] [Indexed: 11/09/2022] Open
Abstract
Quantum Hall edge channels offer an efficient and controllable platform to study quantum transport in one dimension. Such channels are a prospective tool for the efficient transfer of quantum information at the nanoscale, and play a vital role in exposing intriguing physics. Electric current along the edge carries energy and heat leading to inelastic scattering, which may impede coherent transport. Several experiments attempting to probe the concomitant energy redistribution along the edge reported energy loss via unknown mechanisms of inelastic scattering. Here we employ quantum dots to inject and extract electrons at specific energies, to spectrally analyse inelastic scattering inside quantum Hall edge channels. We show that the missing energy puzzle could be untangled by incorporating non-local Auger-like processes, in which energy is redistributed between spatially separate parts of the sample. Our theoretical analysis, accounting for the experimental results, challenges common-wisdom analyses which ignore such non-local decay channels.
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Affiliation(s)
- T Krähenmann
- Solid State Physics Laboratory, ETH Zürich, CH-8093, Zürich, Switzerland.
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2628CJ, the Netherlands.
| | - S G Fischer
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
| | - M Röösli
- Solid State Physics Laboratory, ETH Zürich, CH-8093, Zürich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zürich, CH-8093, Zürich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zürich, CH-8093, Zürich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zürich, CH-8093, Zürich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zürich, CH-8093, Zürich, Switzerland
| | - Y Gefen
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Yigal Meir
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
- The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
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27
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Kurzmann A, Overweg H, Eich M, Pally A, Rickhaus P, Pisoni R, Lee Y, Watanabe K, Taniguchi T, Ihn T, Ensslin K. Charge Detection in Gate-Defined Bilayer Graphene Quantum Dots. Nano Lett 2019; 19:5216-5221. [PMID: 31311270 DOI: 10.1021/acs.nanolett.9b01617] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report on charge detection in electrostatically defined quantum dot devices in bilayer graphene using an integrated charge detector. The device is fabricated without any etching and features a graphite back gate, leading to high-quality quantum dots. The charge detector is based on a second quantum dot separated from the first dot by depletion underneath a 150 nm wide gate. We show that Coulomb resonances in the sensing dot are sensitive to individual charging events on the nearby quantum dot. The potential change due to single electron charging causes a steplike change (up to 77%) in the current through the charge detector. Furthermore, the charging states of a quantum dot with tunable tunneling barriers and of coupled quantum dots can be detected.
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Affiliation(s)
- Annika Kurzmann
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Hiske Overweg
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Marius Eich
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Alessia Pally
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Kenji Watanabe
- National Institute for Material Science , 1-1 Namiki , Tsukuba 30-0044 , Japan
| | - Takashi Taniguchi
- National Institute for Material Science , 1-1 Namiki , Tsukuba 30-0044 , Japan
| | - Thomas Ihn
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
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28
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Kurzmann A, Eich M, Overweg H, Mangold M, Herman F, Rickhaus P, Pisoni R, Lee Y, Garreis R, Tong C, Watanabe K, Taniguchi T, Ensslin K, Ihn T. Excited States in Bilayer Graphene Quantum Dots. Phys Rev Lett 2019; 123:026803. [PMID: 31386494 DOI: 10.1103/physrevlett.123.026803] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Indexed: 05/21/2023]
Abstract
We report ground- and excited-state transport through an electrostatically defined few-hole quantum dot in bilayer graphene in both parallel and perpendicular applied magnetic fields. A remarkably clear level scheme for the two-particle spectra is found by analyzing finite bias spectroscopy data within a two-particle model including spin and valley degrees of freedom. We identify the two-hole ground state to be a spin-triplet and valley-singlet state. This spin alignment can be seen as Hund's rule for a valley-degenerate system, which is fundamentally different from quantum dots in carbon nanotubes, where the two-particle ground state is a spin-singlet state. The spin-singlet excited states are found to be valley-triplet states by tilting the magnetic field with respect to the sample plane. We quantify the exchange energy to be 0.35 meV and measure a valley and spin g factor of 36 and 2, respectively.
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Affiliation(s)
- A Kurzmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M Eich
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - H Overweg
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M Mangold
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - F Herman
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - P Rickhaus
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - R Pisoni
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Y Lee
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - R Garreis
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Tong
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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29
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Landig AJ, Koski JV, Scarlino P, Reichl C, Wegscheider W, Wallraff A, Ensslin K, Ihn T. Microwave-Cavity-Detected Spin Blockade in a Few-Electron Double Quantum Dot. Phys Rev Lett 2019; 122:213601. [PMID: 31283346 DOI: 10.1103/physrevlett.122.213601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Indexed: 06/09/2023]
Abstract
We investigate spin states of few electrons in a double quantum dot by coupling them to a magnetic field resilient NbTiN microwave resonator. The electric field of the resonator couples to the electric dipole moment of the charge states in the double dot. For a two-electron state the spin-triplet state has a vanishing electric dipole moment and can therefore be distinguished from the spin-singlet state. This way the charge dipole sensitivity of the resonator response is converted to a spin selectivity. We thereby investigate Pauli spin blockade known from transport experiments at finite source-drain bias. In addition we find an unconventional spin-blockade triggered by the absorption of resonator photons.
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Affiliation(s)
- A J Landig
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - J V Koski
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - P Scarlino
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - C Reichl
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - W Wegscheider
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - A Wallraff
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - K Ensslin
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T Ihn
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
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30
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Scarlino P, van Woerkom DJ, Stockklauser A, Koski JV, Collodo MC, Gasparinetti S, Reichl C, Wegscheider W, Ihn T, Ensslin K, Wallraff A. All-Microwave Control and Dispersive Readout of Gate-Defined Quantum Dot Qubits in Circuit Quantum Electrodynamics. Phys Rev Lett 2019; 122:206802. [PMID: 31172788 DOI: 10.1103/physrevlett.122.206802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/31/2019] [Indexed: 05/27/2023]
Abstract
Developing fast and accurate control and readout techniques is an important challenge in quantum information processing with semiconductor qubits. Here, we study the dynamics and the coherence properties of a GaAs/AlGaAs double quantum dot charge qubit strongly coupled to a frequency-tunable high-impedance resonator. We drive qubit transitions with synthesized microwave pulses and perform qubit readout through the state-dependent frequency shift imparted by the qubit on the dispersively coupled resonator. We perform Rabi oscillation, Ramsey fringe, energy relaxation, and Hahn-echo measurements and find significantly reduced decoherence rates down to γ_{2}/2π∼3 MHz corresponding to coherence times of up to T_{2}∼50 ns for charge states in gate-defined quantum dot qubits. We realize Rabi π pulses of width down to σ∼0.25 ns.
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Affiliation(s)
- P Scarlino
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - D J van Woerkom
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - A Stockklauser
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - J V Koski
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M C Collodo
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - S Gasparinetti
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - A Wallraff
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
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31
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Overweg H, Knothe A, Fabian T, Linhart L, Rickhaus P, Wernli L, Watanabe K, Taniguchi T, Sánchez D, Burgdörfer J, Libisch F, Fal'ko VI, Ensslin K, Ihn T. Topologically Nontrivial Valley States in Bilayer Graphene Quantum Point Contacts. Phys Rev Lett 2018; 121:257702. [PMID: 30608777 DOI: 10.1103/physrevlett.121.257702] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Indexed: 06/09/2023]
Abstract
We present measurements of quantized conductance in electrostatically induced quantum point contacts in bilayer graphene. The application of a perpendicular magnetic field leads to an intricate pattern of lifted and restored degeneracies with increasing field: at zero magnetic field the degeneracy of quantized one-dimensional subbands is four, because of a twofold spin and a twofold valley degeneracy. By switching on the magnetic field, the valley degeneracy is lifted. Because of the Berry curvature, states from different valleys split linearly in magnetic field. In the quantum Hall regime fourfold degenerate conductance plateaus reemerge. During the adiabatic transition to the quantum Hall regime, levels from one valley shift by two in quantum number with respect to the other valley, forming an interweaving pattern that can be reproduced by numerical calculations.
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Affiliation(s)
- Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Angelika Knothe
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Thomas Fabian
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Lukas Linhart
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Lucien Wernli
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - David Sánchez
- Institute for Cross-Disciplinary Physics and Complex Systems IFISC (UIB-CSIC), 07122 Palma de Mallorca, Spain
| | - Joachim Burgdörfer
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Florian Libisch
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Vladimir I Fal'ko
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
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32
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Pisoni R, Kormányos A, Brooks M, Lei Z, Back P, Eich M, Overweg H, Lee Y, Rickhaus P, Watanabe K, Taniguchi T, Imamoglu A, Burkard G, Ihn T, Ensslin K. Interactions and Magnetotransport through Spin-Valley Coupled Landau Levels in Monolayer MoS_{2}. Phys Rev Lett 2018; 121:247701. [PMID: 30608765 DOI: 10.1103/physrevlett.121.247701] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Indexed: 06/09/2023]
Abstract
The strong spin-orbit coupling and the broken inversion symmetry in monolayer transition metal dichalcogenides results in spin-valley coupled band structures. Such a band structure leads to novel applications in the fields of electronics and optoelectronics. Density functional theory calculations as well as optical experiments have focused on spin-valley coupling in the valence band. Here we present magnetotransport experiments on high-quality n-type monolayer molybdenum disulphide (MoS_{2}) samples, displaying highly resolved Shubnikov-de Haas oscillations at magnetic fields as low as 2 T. We find the effective mass 0.7m_{e}, about twice as large as theoretically predicted and almost independent of magnetic field and carrier density. We further detect the occupation of the second spin-orbit split band at an energy of about 15 meV, i.e., about a factor of 5 larger than predicted. In addition, we demonstrate an intricate Landau level spectrum arising from a complex interplay between a density-dependent Zeeman splitting and spin- and valley-split Landau levels. These observations, enabled by the high electronic quality of our samples, testify to the importance of interaction effects in the conduction band of monolayer MoS_{2}.
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Affiliation(s)
- Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Andor Kormányos
- Department of Physics, University of Konstanz, D-78464 Konstanz, Germany
- Department of Physics of Complex Systems, Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
| | - Matthew Brooks
- Department of Physics, University of Konstanz, D-78464 Konstanz, Germany
| | - Zijin Lei
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Patrick Back
- Institute of Quantum Electronics, Department of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Atac Imamoglu
- Institute of Quantum Electronics, Department of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Guido Burkard
- Department of Physics, University of Konstanz, D-78464 Konstanz, Germany
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
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33
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Rickhaus P, Wallbank J, Slizovskiy S, Pisoni R, Overweg H, Lee Y, Eich M, Liu MH, Watanabe K, Taniguchi T, Ihn T, Ensslin K. Transport Through a Network of Topological Channels in Twisted Bilayer Graphene. Nano Lett 2018; 18:6725-6730. [PMID: 30336041 DOI: 10.1021/acs.nanolett.8b02387] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We explore a network of electronic quantum valley Hall states in the moiré crystal of minimally twisted bilayer graphene. In our transport measurements, we observe Fabry-Pérot and Aharanov-Bohm oscillations that are robust in magnetic fields ranging from 0 to 8 T, which is in strong contrast to more conventional two-dimensional systems where trajectories in the bulk are bent by the Lorentz force. This persistence in magnetic field and the linear spacing in density indicate that charge carriers in the bulk flow in topologically protected, one-dimensional channels. With this work, we demonstrate coherent electronic transport in a lattice of topologically protected states.
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Affiliation(s)
- Peter Rickhaus
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - John Wallbank
- Centre for Ecology and Hydrology , Maclean Building, Benson Lane , Crowmarsh Gifford, Wallingford, Oxfordshire , OX10 8BB , United Kingdom
| | | | - Riccardo Pisoni
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Hiske Overweg
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Yongjin Lee
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Marius Eich
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Ming-Hao Liu
- Department of Physics , National Cheng Kung University , Tainan 70101 , Taiwan
| | - Kenji Watanabe
- National Institute for Material Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Takashi Taniguchi
- National Institute for Material Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Thomas Ihn
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Klaus Ensslin
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
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34
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Eich M, Pisoni R, Pally A, Overweg H, Kurzmann A, Lee Y, Rickhaus P, Watanabe K, Taniguchi T, Ensslin K, Ihn T. Coupled Quantum Dots in Bilayer Graphene. Nano Lett 2018; 18:5042-5048. [PMID: 29985000 DOI: 10.1021/acs.nanolett.8b01859] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Electrostatic confinement of charge carriers in bilayer graphene provides a unique platform for carbon-based spin, charge, or exchange qubits. By exploiting the possibility to induce a band gap with electrostatic gating, we form a versatile and widely tunable multiquantum dot system. We demonstrate the formation of single, double and triple quantum dots that are free of any sign of disorder. In bilayer graphene, we have the possibility to form tunnel barriers using different mechanisms. We can exploit the ambipolar nature of bilayer graphene where pn-junctions form natural tunnel barriers. Alternatively, we can use gates to form tunnel barriers, where we can vary the tunnel coupling by more than 2 orders of magnitude tuning between a deeply Coulomb blockaded system and a Fabry-Pérot-like cavity. Demonstrating such tunability is an important step toward graphene-based quantum computation.
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Affiliation(s)
- Marius Eich
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Alessia Pally
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Hiske Overweg
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Kenji Watanabe
- Advanced Materials Laboratory , NIMS , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory , NIMS , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
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35
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Koski JV, Landig AJ, Pályi A, Scarlino P, Reichl C, Wegscheider W, Burkard G, Wallraff A, Ensslin K, Ihn T. Floquet Spectroscopy of a Strongly Driven Quantum Dot Charge Qubit with a Microwave Resonator. Phys Rev Lett 2018; 121:043603. [PMID: 30095954 DOI: 10.1103/physrevlett.121.043603] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Indexed: 06/08/2023]
Abstract
We experimentally investigate a strongly driven GaAs double quantum dot charge qubit weakly coupled to a superconducting microwave resonator. The Floquet states emerging from strong driving are probed by tracing the qubit-resonator resonance condition. In this way, we probe the resonance of a qubit that is driven in an adiabatic, a nonadiabatic, or an intermediate rate, showing distinct quantum features of multiphoton processes and a fringe pattern similar to Landau-Zener-Stückelberg interference. Our resonant detection scheme enables the investigation of novel features when the drive frequency is comparable to the resonator frequency. Models based on the adiabatic approximation, rotating wave approximation, and Floquet theory explain our experimental observations.
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Affiliation(s)
- J V Koski
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - A J Landig
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - A Pályi
- Department of Physics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
- MTA-BME Exotic Quantum Phases "Momentum" Research Group, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
| | - P Scarlino
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - G Burkard
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - A Wallraff
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
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36
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Landig AJ, Koski JV, Scarlino P, Mendes UC, Blais A, Reichl C, Wegscheider W, Wallraff A, Ensslin K, Ihn T. Coherent spin-photon coupling using a resonant exchange qubit. Nature 2018; 560:179-184. [PMID: 30046114 DOI: 10.1038/s41586-018-0365-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 06/19/2018] [Indexed: 11/09/2022]
Abstract
Electron spins hold great promise for quantum computation because of their long coherence times. Long-distance coherent coupling of spins is a crucial step towards quantum information processing with spin qubits. One approach to realizing interactions between distant spin qubits is to use photons as carriers of quantum information. Here we demonstrate strong coupling between single microwave photons in a niobium titanium nitride high-impedance resonator and a three-electron spin qubit (also known as a resonant exchange qubit) in a gallium arsenide device consisting of three quantum dots. We observe the vacuum Rabi mode splitting of the resonance of the resonator, which is a signature of strong coupling; specifically, we observe a coherent coupling strength of about 31 megahertz and a qubit decoherence rate of about 20 megahertz. We can tune the decoherence electrostatically to obtain a minimal decoherence rate of around 10 megahertz for a coupling strength of around 23 megahertz. We directly measure the dependence of the qubit-photon coupling strength on the tunable electric dipole moment of the qubit using the 'AC Stark' effect. Our demonstration of strong qubit-photon coupling for a three-electron spin qubit is an important step towards coherent long-distance coupling of spin qubits.
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Affiliation(s)
- A J Landig
- Department of Physics, ETH Zürich, Zurich, Switzerland.
| | - J V Koski
- Department of Physics, ETH Zürich, Zurich, Switzerland
| | - P Scarlino
- Department of Physics, ETH Zürich, Zurich, Switzerland
| | - U C Mendes
- Institut quantique and Départment de Physique, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - A Blais
- Institut quantique and Départment de Physique, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,Canadian Institute for Advanced Research, Toronto, Ontario, Canada
| | - C Reichl
- Department of Physics, ETH Zürich, Zurich, Switzerland
| | - W Wegscheider
- Department of Physics, ETH Zürich, Zurich, Switzerland
| | - A Wallraff
- Department of Physics, ETH Zürich, Zurich, Switzerland
| | - K Ensslin
- Department of Physics, ETH Zürich, Zurich, Switzerland
| | - T Ihn
- Department of Physics, ETH Zürich, Zurich, Switzerland
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37
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Hamer M, Tóvári E, Zhu M, Thompson MD, Mayorov A, Prance J, Lee Y, Haley RP, Kudrynskyi ZR, Patanè A, Terry D, Kovalyuk ZD, Ensslin K, Kretinin AV, Geim A, Gorbachev R. Gate-Defined Quantum Confinement in InSe-Based van der Waals Heterostructures. Nano Lett 2018; 18:3950-3955. [PMID: 29763556 DOI: 10.1021/acs.nanolett.8b01376] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Indium selenide, a post-transition metal chalcogenide, is a novel two-dimensional (2D) semiconductor with interesting electronic properties. Its tunable band gap and high electron mobility have already attracted considerable research interest. Here we demonstrate strong quantum confinement and manipulation of single electrons in devices made from few-layer crystals of InSe using electrostatic gating. We report on gate-controlled quantum dots in the Coulomb blockade regime as well as one-dimensional quantization in point contacts, revealing multiple plateaus. The work represents an important milestone in the development of quality devices based on 2D materials and makes InSe a prime candidate for relevant electronic and optoelectronic applications.
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Affiliation(s)
- Matthew Hamer
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Endre Tóvári
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Mengjian Zhu
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Michael D Thompson
- Department of Physics , University of Lancaster , Bailrigg , Lancaster , LA1 4YW , U.K
| | - Alexander Mayorov
- Centre for Advanced 2D Materials , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Jonathon Prance
- Department of Physics , University of Lancaster , Bailrigg , Lancaster , LA1 4YW , U.K
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zurich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Richard P Haley
- Department of Physics , University of Lancaster , Bailrigg , Lancaster , LA1 4YW , U.K
| | - Zakhar R Kudrynskyi
- School of Physics and Astronomy , University of Nottingham , Nottingham NG7 2RD , U.K
| | - Amalia Patanè
- School of Physics and Astronomy , University of Nottingham , Nottingham NG7 2RD , U.K
| | - Daniel Terry
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Zakhar D Kovalyuk
- National Academy of Sciences of Ukraine , Institute for Problems of Materials Science , UA-58001 , Chernovtsy , Ukraine
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zurich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Andrey V Kretinin
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- School of Materials , University of Manchester , Oxford Road , Manchester M13 9PL , U.K
| | - Andre Geim
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Roman Gorbachev
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
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38
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Nicolí G, Ferguson MS, Rössler C, Wolfertz A, Blatter G, Ihn T, Ensslin K, Reichl C, Wegscheider W, Zilberberg O. Cavity-Mediated Coherent Coupling between Distant Quantum Dots. Phys Rev Lett 2018; 120:236801. [PMID: 29932683 DOI: 10.1103/physrevlett.120.236801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Indexed: 06/08/2023]
Abstract
Scalable architectures for quantum information technologies require one to selectively couple long-distance qubits while suppressing environmental noise and cross talk. In semiconductor materials, the coherent coupling of a single spin on a quantum dot to a cavity hosting fermionic modes offers a new solution to this technological challenge. Here, we demonstrate coherent coupling between two spatially separated quantum dots using an electronic cavity design that takes advantage of whispering-gallery modes in a two-dimensional electron gas. The cavity-mediated, long-distance coupling effectively minimizes undesirable direct cross talk between the dots and defines a scalable architecture for all-electronic semiconductor-based quantum information processing.
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Affiliation(s)
- Giorgio Nicolí
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Clemens Rössler
- Infineon Technologies Austria, Siemensstraße 2, 9500 Villach, Austria
| | | | - Gianni Blatter
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Christian Reichl
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Oded Zilberberg
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
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39
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Overweg H, Eggimann H, Chen X, Slizovskiy S, Eich M, Pisoni R, Lee Y, Rickhaus P, Watanabe K, Taniguchi T, Fal'ko V, Ihn T, Ensslin K. Electrostatically Induced Quantum Point Contacts in Bilayer Graphene. Nano Lett 2018; 18:553-559. [PMID: 29286668 DOI: 10.1021/acs.nanolett.7b04666] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the fabrication of electrostatically defined nanostructures in encapsulated bilayer graphene, with leakage resistances below depletion gates as high as R ∼ 10 GΩ. This exceeds previously reported values of R = 10-100 kΩ.1-3 We attribute this improvement to the use of a graphite back gate. We realize two split gate devices which define an electronic channel on the scale of the Fermi-wavelength. A channel gate covering the gap between the split gates varies the charge carrier density in the channel. We observe device-dependent conductance quantization of ΔG = 2e2/h and ΔG = 4e2/h. In quantizing magnetic fields normal to the sample plane, we recover the four-fold Landau level degeneracy of bilayer graphene. Unexpected mode crossings appear at the crossover between zero magnetic field and the quantum Hall regime.
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Affiliation(s)
- Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Hannah Eggimann
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Xi Chen
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Sergey Slizovskiy
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science ,1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science ,1-1 Namiki, Tsukuba 305-0044, Japan
| | | | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
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40
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Hofmann A, Maisi VF, Krähenmann T, Reichl C, Wegscheider W, Ensslin K, Ihn T. Anisotropy and Suppression of Spin-Orbit Interaction in a GaAs Double Quantum Dot. Phys Rev Lett 2017; 119:176807. [PMID: 29219432 DOI: 10.1103/physrevlett.119.176807] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Indexed: 06/07/2023]
Abstract
The spin-flip tunneling rates are measured in GaAs-based double quantum dots by time-resolved charge detection. Such processes occur in the Pauli spin blockade regime with two electrons occupying the double quantum dot. Ways are presented for tuning the spin-flip tunneling rate, which on the one hand gives access to measuring the Rashba and Dresselhaus spin-orbit coefficients. On the other hand, they make it possible to turn on and off the effect of spin-orbit interaction with a high on/off ratio. The tuning is accomplished by choosing the alignment of the tunneling direction with respect to the crystallographic axes, as well as by choosing the orientation of the external magnetic field with respect to the spin-orbit magnetic field. Spin lifetimes of 10 s are achieved at a tunneling rate close to 1 kHz.
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Affiliation(s)
- A Hofmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - V F Maisi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Krähenmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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41
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Pisoni R, Lee Y, Overweg H, Eich M, Simonet P, Watanabe K, Taniguchi T, Gorbachev R, Ihn T, Ensslin K. Gate-Defined One-Dimensional Channel and Broken Symmetry States in MoS 2 van der Waals Heterostructures. Nano Lett 2017; 17:5008-5011. [PMID: 28686030 DOI: 10.1021/acs.nanolett.7b02186] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We have realized encapsulated trilayer MoS2 devices with gated graphene contacts. In the bulk, we observe an electron mobility as high as 7000 cm2/(V s) at a density of 3 × 1012 cm-2 at a temperature of 1.9 K. Shubnikov-de Haas oscillations start at magnetic fields as low as 0.9 T. The observed 3-fold Landau level degeneracy can be understood based on the valley Zeeman effect. Negatively biased split gate electrodes allow us to form a channel that can be completely pinched off for sufficiently large gate voltages. The measured conductance displays plateau-like features.
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Affiliation(s)
- Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Pauline Simonet
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Roman Gorbachev
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
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42
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Karalic M, Mittag C, Tschirky T, Wegscheider W, Ensslin K, Ihn T. Lateral p-n Junction in an Inverted InAs/GaSb Double Quantum Well. Phys Rev Lett 2017; 118:206801. [PMID: 28581788 DOI: 10.1103/physrevlett.118.206801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Indexed: 06/07/2023]
Abstract
We present transport measurements on a lateral p-n junction in an inverted InAs/GaSb double quantum well at zero and nonzero perpendicular magnetic fields. At a zero magnetic field, the junction exhibits diodelike behavior in accordance with the presence of a hybridization gap. With an increasing magnetic field, we explore the quantum Hall regime where spin-polarized edge states with the same chirality are either reflected or transmitted at the junction, whereas those of opposite chirality undergo a mixing process, leading to full equilibration along the width of the junction independent of spin. These results lay the foundations for using p-n junctions in InAs/GaSb double quantum wells to probe the transition between the topological quantum spin Hall and quantum Hall states.
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Affiliation(s)
- Matija Karalic
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | | | - Thomas Tschirky
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | | | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
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43
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Overweg H, Eggimann H, Liu MH, Varlet A, Eich M, Simonet P, Lee Y, Watanabe K, Taniguchi T, Richter K, Fal'ko VI, Ensslin K, Ihn T. Oscillating Magnetoresistance in Graphene p-n Junctions at Intermediate Magnetic Fields. Nano Lett 2017; 17:2852-2857. [PMID: 28383919 DOI: 10.1021/acs.nanolett.6b05318] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report on the observation of magnetoresistance oscillations in graphene p-n junctions. The oscillations have been observed for six samples, consisting of single-layer and bilayer graphene, and persist up to temperatures of 30 K, where standard Shubnikov-de Haas oscillations are no longer discernible. The oscillatory magnetoresistance can be reproduced by tight-binding simulations. We attribute this phenomenon to the modulated densities of states in the n- and p-regions.
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Affiliation(s)
- Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Hannah Eggimann
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Ming-Hao Liu
- Institut für Theoretische Physik, Universität Regensburg , D-93040 Regensburg, Germany
- Department of Physics, National Cheng Kung University , Tainan 70101, Taiwan
| | - Anastasia Varlet
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Pauline Simonet
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Kenji Watanabe
- Advanced Materials Laboratory, National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory, National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Klaus Richter
- Institut für Theoretische Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Vladimir I Fal'ko
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
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44
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Hofmann A, Maisi VF, Gold C, Krähenmann T, Rössler C, Basset J, Märki P, Reichl C, Wegscheider W, Ensslin K, Ihn T. Measuring the Degeneracy of Discrete Energy Levels Using a GaAs/AlGaAs Quantum Dot. Phys Rev Lett 2016; 117:206803. [PMID: 27886466 DOI: 10.1103/physrevlett.117.206803] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Indexed: 06/06/2023]
Abstract
We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance and the ability to perform precise and efficient measurements of energy-dependent tunneling-in and -out rates from a reservoir. The method is realized using a GaAs/AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunneling with a precision enhanced by a feedback control. It is thoroughly tested by tuning orbital and spin degeneracies with electric and magnetic fields. The technique also lends itself to studying the connection between the ground-state degeneracy and the lifetime of the excited states.
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Affiliation(s)
- A Hofmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - V F Maisi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Gold
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Krähenmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Rössler
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - J Basset
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - P Märki
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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45
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Maisi VF, Hofmann A, Röösli M, Basset J, Reichl C, Wegscheider W, Ihn T, Ensslin K. Spin-Orbit Coupling at the Level of a Single Electron. Phys Rev Lett 2016; 116:136803. [PMID: 27081997 DOI: 10.1103/physrevlett.116.136803] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Indexed: 06/05/2023]
Abstract
We utilize electron counting techniques to distinguish a spin-conserving fast tunneling process and a slower process involving spin flips in AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates on the interdot tunnel coupling of the two dots, we find that as many as 4% of the tunneling events occur with a spin flip related to spin-orbit coupling in GaAs. Our measurement has a fidelity of 99% in terms of resolving whether a tunneling event occurred with a spin flip or not.
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Affiliation(s)
- V F Maisi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - A Hofmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M Röösli
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - J Basset
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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46
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Hennel S, Braem BA, Baer S, Tiemann L, Sohi P, Wehrli D, Hofmann A, Reichl C, Wegscheider W, Rössler C, Ihn T, Ensslin K, Rudner MS, Rosenow B. Nonlocal Polarization Feedback in a Fractional Quantum Hall Ferromagnet. Phys Rev Lett 2016; 116:136804. [PMID: 27081998 DOI: 10.1103/physrevlett.116.136804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Indexed: 06/05/2023]
Abstract
In a quantum Hall ferromagnet, the spin polarization of the two-dimensional electron system can be dynamically transferred to nuclear spins in its vicinity through the hyperfine interaction. The resulting nuclear field typically acts back locally, modifying the local electronic Zeeman energy. Here we report a nonlocal effect arising from the interplay between nuclear polarization and the spatial structure of electronic domains in a ν=2/3 fractional quantum Hall state. In our experiments, we use a quantum point contact to locally control and probe the domain structure of different spin configurations emerging at the spin phase transition. Feedback between nuclear and electronic degrees of freedom gives rise to memristive behavior, where electronic transport through the quantum point contact depends on the history of current flow. We propose a model for this effect which suggests a novel route to studying edge states in fractional quantum Hall systems and may account for so-far unexplained oscillatory electronic-transport features observed in previous studies.
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Affiliation(s)
- Szymon Hennel
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Beat A Braem
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Stephan Baer
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Lars Tiemann
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Pirouz Sohi
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Dominik Wehrli
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Andrea Hofmann
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Christian Reichl
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Clemens Rössler
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Mark S Rudner
- Niels Bohr International Academy and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Bernd Rosenow
- Institut für Theoretische Physik, Universität Leipzig, D-04009 Leipzig, Germany
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47
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Kozikov AA, Steinacher R, Rössler C, Ihn T, Ensslin K, Reichl C, Wegscheider W. Mode Specific Backscattering in a Quantum Point Contact. Nano Lett 2015; 15:7994-7999. [PMID: 26569040 DOI: 10.1021/acs.nanolett.5b03170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate a scanning gate grid measurement technique consisting in measuring the conductance of a quantum point contact (QPC) as a function of gate voltage at each tip position. Unlike conventional scanning gate experiments, it allows investigating QPC conductance plateaus affected by the tip at these positions. We compensate the capacitive coupling of the tip to the QPC and discover that interference fringes coexist with distorted QPC plateaus. We spatially resolve the mode structure for each plateau.
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Affiliation(s)
- A A Kozikov
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - R Steinacher
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - C Rössler
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
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48
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Rössler C, Oehri D, Zilberberg O, Blatter G, Karalic M, Pijnenburg J, Hofmann A, Ihn T, Ensslin K, Reichl C, Wegscheider W. Transport Spectroscopy of a Spin-Coherent Dot-Cavity System. Phys Rev Lett 2015; 115:166603. [PMID: 26550890 DOI: 10.1103/physrevlett.115.166603] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 06/05/2023]
Abstract
Quantum engineering requires controllable artificial systems with quantum coherence exceeding the device size and operation time. This can be achieved with geometrically confined low-dimensional electronic structures embedded within ultraclean materials, with prominent examples being artificial atoms (quantum dots) and quantum corrals (electronic cavities). Combining the two structures, we implement a mesoscopic coupled dot-cavity system in a high-mobility two-dimensional electron gas, and obtain an extended spin-singlet state in the regime of strong dot-cavity coupling. Engineering such extended quantum states presents a viable route for nonlocal spin coupling that is applicable for quantum information processing.
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Affiliation(s)
- C Rössler
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - D Oehri
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - O Zilberberg
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - G Blatter
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - M Karalic
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - J Pijnenburg
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - A Hofmann
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
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49
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Abstract
We present an electronic transport experiment in graphene where both classical and quantum mechanical charge detector back-action on a quantum dot are investigated. The device consists of two stacked graphene quantum dots separated by a thin layer of boron nitride. This device is fabricated by van der Waals stacking and is equipped with separate source and drain contacts to both dots. By applying a finite bias to one quantum dot, a current is induced in the other unbiased dot. We present an explanation of the observed measurement-induced current based on strong capacitive coupling and energy dependent tunneling barriers, breaking the spatial symmetry in the unbiased system. This is a special feature of graphene-based quantum devices. The experimental observation of transport in classically forbidden regimes is understood by considering higher-order quantum mechanical back-action mechanisms.
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Affiliation(s)
- D Bischoff
- Solid State Physics Laboratory and ‡Institute for Theoretical Physics, ETH Zurich , 8093 Zurich, Switzerland
| | - M Eich
- Solid State Physics Laboratory and ‡Institute for Theoretical Physics, ETH Zurich , 8093 Zurich, Switzerland
| | - O Zilberberg
- Solid State Physics Laboratory and ‡Institute for Theoretical Physics, ETH Zurich , 8093 Zurich, Switzerland
| | - C Rössler
- Solid State Physics Laboratory and ‡Institute for Theoretical Physics, ETH Zurich , 8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory and ‡Institute for Theoretical Physics, ETH Zurich , 8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory and ‡Institute for Theoretical Physics, ETH Zurich , 8093 Zurich, Switzerland
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50
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Stockklauser A, Maisi VF, Basset J, Cujia K, Reichl C, Wegscheider W, Ihn T, Wallraff A, Ensslin K. Microwave Emission from Hybridized States in a Semiconductor Charge Qubit. Phys Rev Lett 2015; 115:046802. [PMID: 26252704 DOI: 10.1103/physrevlett.115.046802] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Indexed: 05/27/2023]
Abstract
We explore the microwave radiation emitted from a biased double quantum dot due to the inelastic tunneling of single charges. Radiation is detected over a broad range of detuning configurations between the dot energy levels, with pronounced maxima occurring in resonance with a capacitively coupled transmission line resonator. The power emitted for forward and reverse resonant detuning is found to be in good agreement with a rate equation model, which considers the hybridization of the individual dot charge states.
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Affiliation(s)
- A Stockklauser
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - V F Maisi
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - J Basset
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - K Cujia
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - A Wallraff
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Department of Physics, ETH Zürich, CH-8093 Zurich, Switzerland
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