1
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Aspegren M, Chergui L, Marnauza M, Debbarma R, Bengtsson J, Lehmann S, Dick KA, Reimann SM, Thelander C. Perfect Zeeman Anisotropy in Rotationally Symmetric Quantum Dots with Strong Spin-Orbit Interaction. NANO LETTERS 2024; 24:7927-7933. [PMID: 38885648 PMCID: PMC11229058 DOI: 10.1021/acs.nanolett.4c01247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 06/05/2024] [Accepted: 06/05/2024] [Indexed: 06/20/2024]
Abstract
In nanoscale structures with rotational symmetry, such as quantum rings, the orbital motion of electrons combined with a spin-orbit interaction can produce a very strong and anisotropic Zeeman effect. Since symmetry is sensitive to electric fields, ring-like geometries provide an opportunity to manipulate magnetic properties over an exceptionally wide range. In this work, we show that it is possible to form rotationally symmetric confinement potentials inside a semiconductor quantum dot, resulting in electron orbitals with large orbital angular momentum and strong spin-orbit interactions. We find complete suppression of Zeeman spin splitting for magnetic fields applied in the quantum dot plane, similar to the expected behavior of an ideal quantum ring. Spin splitting reappears as orbital interactions are activated with symmetry-breaking electric fields. For two valence electrons, representing a common basis for spin-qubits, we find that modulating the rotational symmetry may offer new prospects for realizing tunable protection and interaction of spin-orbital states.
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Affiliation(s)
- Markus Aspegren
- Solid State Physics and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | - Lila Chergui
- Mathematical Physics and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | - Mikelis Marnauza
- Centre for Analysis and Synthesis and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | - Rousan Debbarma
- Solid State Physics and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | - Jakob Bengtsson
- Mathematical Physics and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | - Sebastian Lehmann
- Solid State Physics and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | - Kimberly A Dick
- Centre for Analysis and Synthesis and NanoLund, Lund University, SE-221 00 Lund, Sweden
| | | | - Claes Thelander
- Solid State Physics and NanoLund, Lund University, SE-221 00 Lund, Sweden
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2
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Badawy G, Bakkers EPAM. Electronic Transport and Quantum Phenomena in Nanowires. Chem Rev 2024; 124:2419-2440. [PMID: 38394689 PMCID: PMC10941195 DOI: 10.1021/acs.chemrev.3c00656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 01/26/2024] [Accepted: 02/08/2024] [Indexed: 02/25/2024]
Abstract
Nanowires are natural one-dimensional channels and offer new opportunities for advanced electronic quantum transport experiments. We review recent progress on the synthesis of nanowires and methods for the fabrication of hybrid semiconductor/superconductor systems. We discuss methods to characterize their electronic properties in the context of possible future applications such as topological and spin qubits. We focus on group III-V (InAs and InSb) and group IV (Ge/Si) semiconductors, since these are the most developed, and give an outlook on other potential materials.
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Affiliation(s)
- Ghada Badawy
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Erik P. A. M. Bakkers
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
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3
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Bargerbos A, Pita-Vidal M, Žitko R, Splitthoff LJ, Grünhaupt L, Wesdorp JJ, Liu Y, Kouwenhoven LP, Aguado R, Andersen CK, Kou A, van Heck B. Spectroscopy of Spin-Split Andreev Levels in a Quantum Dot with Superconducting Leads. PHYSICAL REVIEW LETTERS 2023; 131:097001. [PMID: 37721843 DOI: 10.1103/physrevlett.131.097001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 07/27/2023] [Indexed: 09/20/2023]
Abstract
We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of a quantum dot Josephson junction tuned to be in a spin-1/2 ground state with an unpaired quasiparticle. Because of spin-orbit coupling, we resolve two flux-sensitive branches in the transmon spectrum, depending on the spin of the quasiparticle. A finite magnetic field shifts the two branches in energy, favoring one spin state and resulting in the anomalous Josephson effect. We demonstrate the excitation of the direct spin-flip transition using all-electrical control. Manipulation and control of the spin-flip transition enable the future implementation of charging energy protected Andreev spin qubits.
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Affiliation(s)
- Arno Bargerbos
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Marta Pita-Vidal
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Rok Žitko
- Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
| | - Lukas J Splitthoff
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Lukas Grünhaupt
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Jaap J Wesdorp
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Yu Liu
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Leo P Kouwenhoven
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Ramón Aguado
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain
| | | | - Angela Kou
- Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Bernard van Heck
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, Netherlands
- Dipartimento di Fisica, Università di Roma "La Sapienza", P.le Aldo Moro 5, 00185 Roma, Italy
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4
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Lozano MS, Gómez VJ. Epitaxial growth of crystal phase quantum dots in III-V semiconductor nanowires. NANOSCALE ADVANCES 2023; 5:1890-1909. [PMID: 36998660 PMCID: PMC10044505 DOI: 10.1039/d2na00956k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 03/06/2023] [Indexed: 06/19/2023]
Abstract
Crystal phase quantum dots (QDs) are formed during the axial growth of III-V semiconductor nanowires (NWs) by stacking different crystal phases of the same material. In III-V semiconductor NWs, both zinc blende (ZB) and wurtzite (WZ) crystal phases can coexist. The band structure difference between both crystal phases can lead to quantum confinement. Thanks to the precise control in III-V semiconductor NW growth conditions and the deep knowledge on the epitaxial growth mechanisms, it is nowadays possible to control, down to the atomic level, the switching between crystal phases in NWs forming the so-called crystal phase NW-based QDs (NWQDs). The shape and size of the NW bridge the gap between QDs and the macroscopic world. This review is focused on crystal phase NWQDs based on III-V NWs obtained by the bottom-up vapor-liquid-solid (VLS) method and their optical and electronic properties. Crystal phase switching can be achieved in the axial direction. In contrast, in the core/shell growth, the difference in surface energies between different polytypes can enable selective shell growth. One reason for the very intense research in this field is motivated by their excellent optical and electronic properties both appealing for applications in nanophotonics and quantum technologies.
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Affiliation(s)
- Miguel Sinusia Lozano
- Nanophotonics Technology Center, Universitat Politècnica de València, Camino de Vera s/n Building 8F, 2a Floor 46022 Valencia Spain
| | - Víctor J Gómez
- Nanophotonics Technology Center, Universitat Politècnica de València, Camino de Vera s/n Building 8F, 2a Floor 46022 Valencia Spain
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5
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Takiguchi K, Anh LD, Chiba T, Shiratani H, Fukuzawa R, Takahashi T, Tanaka M. Giant gate-controlled odd-parity magnetoresistance in one-dimensional channels with a magnetic proximity effect. Nat Commun 2022; 13:6538. [PMID: 36351909 PMCID: PMC9646711 DOI: 10.1038/s41467-022-34177-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 10/13/2022] [Indexed: 11/10/2022] Open
Abstract
According to Onsager's principle, electrical resistance R of general conductors behaves as an even function of external magnetic field B. Only in special circumstances, which involve time reversal symmetry (TRS) broken by ferromagnetism, the odd component of R against B is observed. This unusual phenomenon, called odd-parity magnetoresistance (OMR), was hitherto subtle (< 2%) and hard to control by external means. Here, we report a giant OMR as large as 27% in edge transport channels of an InAs quantum well, which is magnetized by a proximity effect from an underlying ferromagnetic semiconductor (Ga,Fe)Sb layer. Combining experimental results and theoretical analysis using the linearized Boltzmann's equation, we found that simultaneous breaking of both the TRS by the magnetic proximity effect (MPE) and spatial inversion symmetry (SIS) in the one-dimensional (1D) InAs edge channels is the origin of this giant OMR. We also demonstrated the ability to turn on and off the OMR using electrical gating of either TRS or SIS in the edge channels. These findings provide a deep insight into the 1D semiconducting system with a strong magnetic coupling.
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Affiliation(s)
- Kosuke Takiguchi
- Department of Electrical Engineering and Information Systems, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Le Duc Anh
- Department of Electrical Engineering and Information Systems, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Institute of Engineering Innovation, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan.
- Centre for Spintronics Research Network, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Takahiro Chiba
- National Institute of Technology, Fukushima College, Iwaki, Fukushima, 970-8034, Japan
| | - Harunori Shiratani
- Department of Electrical Engineering and Information Systems, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Ryota Fukuzawa
- Department of Electrical Engineering and Information Systems, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan
| | - Takuji Takahashi
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan
- Institute for Nano Quantum Information Electronics, The University of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information Systems, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Centre for Spintronics Research Network, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Institute for Nano Quantum Information Electronics, The University of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan.
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6
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Li W, Mu J, Liu ZH, Huang S, Pan D, Chen Y, Wang JY, Zhao J, Xu HQ. Charge detection of a quantum dot under different tunneling barrier symmetries and bias voltages. NANOSCALE 2022; 14:14029-14037. [PMID: 36048093 DOI: 10.1039/d2nr03459j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We report the realization of a coupled quantum dot (QD) system containing two single QDs made in two adjacent InAs nanowires. One QD (sensor QD) was used as a charge sensor to detect the charge state transitions in the other QD (target QD). We investigated the effect of the tunneling barrier asymmetry of the target QD on the detection visibility of the charge state transitions in the target QD. The charge stability diagrams of the target QD under different configurations of barrier-gate voltages were simultaneously measured via the direct signals of electron transport through the target QD and via the detection signals of the charge state transitions in the target QD revealed by the sensor QD. We find that the complete Coulomb diamond boundaries of the target QD and the transport processes involving the excited states in the target QD can be observed in the transconductance signals of the sensor QD only when the tunneling barriers of the target QD are nearly symmetric. These observations were explained by analyzing the effect of the ratio of the two tunneling rates on the electron transport processes through the target QD. Our results imply that it is important to consider the symmetry of the tunnel couplings when constructing a charge sensor integrated QD device.
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Affiliation(s)
- Weijie Li
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Jingwei Mu
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Zhi-Hai Liu
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Dong Pan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
| | - Yuanjie Chen
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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7
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ten Kate S, Ritter MF, Fuhrer A, Jung J, Schellingerhout SG, Bakkers EPAM, Riel H, Nichele F. Small Charging Energies and g-Factor Anisotropy in PbTe Quantum Dots. NANO LETTERS 2022; 22:7049-7056. [PMID: 35998346 PMCID: PMC9479220 DOI: 10.1021/acs.nanolett.2c01943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 08/15/2022] [Indexed: 06/15/2023]
Abstract
PbTe is a semiconductor with promising properties for topological quantum computing applications. Here, we characterize electron quantum dots in PbTe nanowires selectively grown on InP. Charge stability diagrams at zero magnetic field reveal large even-odd spacing between Coulomb blockade peaks, charging energies below 140 μeV and Kondo peaks in odd Coulomb diamonds. We attribute the large even-odd spacing to the large dielectric constant and small effective electron mass of PbTe. By studying the Zeeman-induced level and Kondo splitting in finite magnetic fields, we extract the electron g-factor as a function of magnetic field direction. We find the g-factor tensor to be highly anisotropic with principal g-factors ranging from 0.9 to 22.4 and to depend on the electronic configuration of the devices. These results indicate strong Rashba spin-orbit interaction in our PbTe quantum dots.
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Affiliation(s)
- Sofieke
C. ten Kate
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
- University
of Twente, Drienerlolaan
5, 7522 NB Enschede, Netherlands
| | - Markus F. Ritter
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Andreas Fuhrer
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Jason Jung
- Eindhoven
University of Technology, 5600 MB Eindhoven, The Netherlands
| | | | | | - Heike Riel
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Fabrizio Nichele
- IBM
Research Europe, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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8
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An SJ, Bae MH, Lee MJ, Song MS, Madsen MH, Nygård J, Schönenberger C, Baumgartner A, Seo J, Jung M. Impact of the gate geometry on adiabatic charge pumping in InAs double quantum dots. NANOSCALE ADVANCES 2022; 4:3816-3823. [PMID: 36133323 PMCID: PMC9470037 DOI: 10.1039/d2na00372d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 08/10/2022] [Indexed: 06/16/2023]
Abstract
We compare the adiabatic quantized charge pumping performed in two types of InAs nanowire double quantum dots (DQDs), either with tunnel barriers defined by closely spaced narrow bottom gates, or by well-separated side gates. In the device with an array of bottom gates of 100 nm pitch and 10 μm lengths, the pump current is quantized only up to frequencies of a few MHz due to the strong capacitive coupling between the bottom gates. In contrast, in devices with well-separated side gates with reduced mutual gate capacitances, we find well-defined pump currents up to 30 MHz. Our experiments demonstrate that high frequency quantized charge pumping requires careful optimization of the device geometry, including the typically neglected gate feed lines.
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Affiliation(s)
- Sung Jin An
- DGIST Research Institute, DGIST Daegu 42988 Korea
- Department of Emerging Materials Science, DGIST Daegu 42988 Korea
| | - Myung-Ho Bae
- Korea Research Institute of Standards and Science Daejeon 34113 Korea
| | - Myoung-Jae Lee
- DGIST Research Institute, DGIST Daegu 42988 Korea
- Institute of Next Generation Semiconductor Technology (INST), DGIST Daegu 42988 Korea
- Department of Interdisciplinary Engineering, DGIST Daegu 42988 Korea
| | - Man Suk Song
- DGIST Research Institute, DGIST Daegu 42988 Korea
- Department of Emerging Materials Science, DGIST Daegu 42988 Korea
| | - Morten H Madsen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen 2100 Copenhagen Denmark
| | - Jesper Nygård
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen 2100 Copenhagen Denmark
| | - Christian Schönenberger
- Department of Physics, University of Basel Klingelbergstrasse 82 CH-4056 Basel Switzerland
- Swiss Nanoscience Institute (SNI), University of Basel Klingelbergstrasse 82 CH-4056 Basel Switzerland
| | - Andreas Baumgartner
- Department of Physics, University of Basel Klingelbergstrasse 82 CH-4056 Basel Switzerland
- Swiss Nanoscience Institute (SNI), University of Basel Klingelbergstrasse 82 CH-4056 Basel Switzerland
| | - Jungpil Seo
- Department of Emerging Materials Science, DGIST Daegu 42988 Korea
- Institute of Next Generation Semiconductor Technology (INST), DGIST Daegu 42988 Korea
| | - Minkyung Jung
- DGIST Research Institute, DGIST Daegu 42988 Korea
- Institute of Next Generation Semiconductor Technology (INST), DGIST Daegu 42988 Korea
- Department of Interdisciplinary Engineering, DGIST Daegu 42988 Korea
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9
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Mu J, Huang S, Liu ZH, Li W, Wang JY, Pan D, Huang GY, Chen Y, Zhao J, Xu HQ. A highly tunable quadruple quantum dot in a narrow bandgap semiconductor InAs nanowire. NANOSCALE 2021; 13:3983-3990. [PMID: 33595588 DOI: 10.1039/d0nr08655j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum dots (QDs) made from semiconductors are among the most promising platforms for the development of quantum computing and simulation chips, and they have the advantages of high density integration and compatibility with the standard semiconductor chip fabrication technology compared to other platforms. However, the development of a highly tunable semiconductor multiple QD system still remains a major challenge. Here, we demonstrate the realization of a highly tunable linear quadruple QD (QQD) in a narrow bandgap semiconductor InAs nanowire via a fine finger gate technique. The QQD is studied by electron transport measurements in the linear response regime. Characteristic two-dimensional charge stability diagrams containing four groups of resonant current lines of different slopes are obtained for the QQD. It is shown that these current lines arise from and can be individually assigned to resonant electron transport through the energy levels of different QDs. Benefitting from the excellent gate tunability, we also demonstrate the tuning of the QQD to regimes where the energy levels of two QDs, three QDs and all four QDs are energetically in resonance, respectively, with the Fermi level of the source and drain contacts. A capacitance network model is developed for the linear QQD and the simulated charge stability diagrams based on this model show good agreement with the experiments. Our work provides solid experimental evidence that narrow bandgap semiconductor nanowire multiple QDs could be used as a versatile platform to achieve integrated qubits for quantum computing and to perform quantum simulations of complex many-body systems.
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Affiliation(s)
- Jingwei Mu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China and Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Zhi-Hai Liu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Weijie Li
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China and Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
| | - Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Dong Pan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China. and Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Guang-Yao Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Yuanjie Chen
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China. and Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China and Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China. and Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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10
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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 LETTERS 2021; 21:1068-1073. [PMID: 33449702 DOI: 10.1021/acs.nanolett.0c04343] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [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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11
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Mu J, Huang S, Wang JY, Huang GY, Wang X, Xu HQ. Measurements of anisotropic g-factors for electrons in InSb nanowire quantum dots. NANOTECHNOLOGY 2021; 32:020002. [PMID: 32987368 DOI: 10.1088/1361-6528/abbc24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We have measured the Zeeman splitting of quantum levels in few-electron quantum dots (QDs) formed in narrow bandgap InSb nanowires via the Schottky barriers at the contacts under application of different spatially orientated magnetic fields. The effective g-factor tensor extracted from the measurements is strongly anisotropic and level-dependent, which can be attributed to the presence of strong spin-orbit interaction (SOI) and asymmetric quantum confinement potentials in the QDs. We have demonstrated a successful determination of the principal values and the principal axis orientations of the g-factor tensors in an InSb nanowire QD by the measurements under rotations of a magnetic field in the three orthogonal planes. We also examine the magnetic field evolution of the excitation spectra in an InSb nanowire QD and extract a SOI strength of [Formula: see text] ∼ 180 μeV from an avoided level crossing between a ground state and its neighboring first excited state in the QD.
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Affiliation(s)
- Jingwei Mu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, People's Republic of China
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
| | - Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
| | - Guang-Yao Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
| | - Xuming Wang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, People's Republic of China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, People's Republic of China
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12
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Potts H, Chen IJ, Tsintzis A, Nilsson M, Lehmann S, Dick KA, Leijnse M, Thelander C. Electrical control of spins and giant g-factors in ring-like coupled quantum dots. Nat Commun 2019; 10:5740. [PMID: 31844044 PMCID: PMC6915759 DOI: 10.1038/s41467-019-13583-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 11/11/2019] [Indexed: 11/09/2022] Open
Abstract
Emerging theoretical concepts for quantum technologies have driven a continuous search for structures where a quantum state, such as spin, can be manipulated efficiently. Central to many concepts is the ability to control a system by electric and magnetic fields, relying on strong spin-orbit interaction and a large g-factor. Here, we present a mechanism for spin and orbital manipulation using small electric and magnetic fields. By hybridizing specific quantum dot states at two points inside InAs nanowires, nearly perfect quantum rings form. Large and highly anisotropic effective g-factors are observed, explained by a strong orbital contribution. Importantly, we find that the orbital contributions can be efficiently quenched by simply detuning the individual quantum dot levels with an electric field. In this way, we demonstrate not only control of the effective g-factor from 80 to almost 0 for the same charge state, but also electrostatic change of the ground state spin.
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Affiliation(s)
- H Potts
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden.
| | - I-J Chen
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - A Tsintzis
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - M Nilsson
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - S Lehmann
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - K A Dick
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
- Centre for Analysis and Synthesis, Lund University, SE-221 00, Lund, Sweden
| | - M Leijnse
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden
| | - C Thelander
- Division of Solid State Physics and NanoLund, Lund University, SE-221 00, Lund, Sweden.
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13
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Gill ST, Damasco J, Janicek BE, Durkin MS, Humbert V, Gazibegovic S, Car D, Bakkers EPAM, Huang PY, Mason N. Selective-Area Superconductor Epitaxy to Ballistic Semiconductor Nanowires. NANO LETTERS 2018; 18:6121-6128. [PMID: 30200769 DOI: 10.1021/acs.nanolett.8b01534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Semiconductor nanowires such as InAs and InSb are promising materials for studying Majorana zero modes and demonstrating non-Abelian particle exchange relevant for topological quantum computing. While evidence for Majorana bound states in nanowires has been shown, the majority of these experiments are marked by significant disorder. In particular, the interfacial inhomogeneity between the superconductor and nanowire is strongly believed to be the main culprit for disorder and the resulting "soft superconducting gap" ubiquitous in tunneling studies of hybrid semiconductor-superconductor systems. Additionally, a lack of ballistic transport in nanowire systems can create bound states that mimic Majorana signatures. We resolve these problems through the development of selective-area epitaxy of Al to InSb nanowires, a technique applicable to other nanowires and superconductors. Epitaxial InSb-Al devices generically possess a hard superconducting gap and demonstrate ballistic 1D superconductivity and near-perfect transmission of supercurrents in the single mode regime, requisites for engineering and controlling 1D topological superconductivity. Additionally, we demonstrate that epitaxial InSb-Al superconducting island devices, the building blocks for Majorana-based quantum computing applications, prepared using selective-area epitaxy can achieve micron-scale ballistic 1D transport. Our results pave the way for the development of networks of ballistic superconducting electronics for quantum device applications.
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Affiliation(s)
| | | | | | | | | | - Sasa Gazibegovic
- QuTech and Kavli Institute of NanoScience , Delft University of Technology , 2600 GA Delft , The Netherlands
- Department of Applied Physics , Eindhoven University of Technology , 5600 MB Eindhoven , The Netherlands
| | - Diana Car
- QuTech and Kavli Institute of NanoScience , Delft University of Technology , 2600 GA Delft , The Netherlands
- Department of Applied Physics , Eindhoven University of Technology , 5600 MB Eindhoven , The Netherlands
| | - Erik P A M Bakkers
- QuTech and Kavli Institute of NanoScience , Delft University of Technology , 2600 GA Delft , The Netherlands
- Department of Applied Physics , Eindhoven University of Technology , 5600 MB Eindhoven , The Netherlands
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14
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Vaitiekėnas S, Deng MT, Nygård J, Krogstrup P, Marcus CM. Effective g Factor of Subgap States in Hybrid Nanowires. PHYSICAL REVIEW LETTERS 2018; 121:037703. [PMID: 30085813 DOI: 10.1103/physrevlett.121.037703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/16/2017] [Indexed: 06/08/2023]
Abstract
We use the effective g factor of Andreev subgap states in an axial magnetic field to investigate how the superconducting density of states is distributed between the semiconductor core and the superconducting shell in hybrid nanowires. We find a steplike reduction of the Andreev g factor and an improved hard gap with reduced carrier density in the nanowire, controlled by gate voltage. These observations are relevant for Majorana devices, which require tunable carrier density and a g factor exceeding that of the parent superconductor.
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Affiliation(s)
- S Vaitiekėnas
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - M-T Deng
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - J Nygård
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - P Krogstrup
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - C M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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15
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Assouline A, Feuillet-Palma C, Zimmers A, Aubin H, Aprili M, Harmand JC. Shiba Bound States across the Mobility Edge in Doped InAs Nanowires. PHYSICAL REVIEW LETTERS 2017; 119:097701. [PMID: 28949581 DOI: 10.1103/physrevlett.119.097701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Indexed: 06/07/2023]
Abstract
We present a study of Andreev quantum dots fabricated with small-diameter (30 nm) Si-doped InAs nanowires where the Fermi level can be tuned across a mobility edge separating localized states from delocalized states. The transition to the insulating phase is identified by a drop in the amplitude and width of the excited levels and is found to have remarkable consequences on the spectrum of superconducting subgap resonances. While at deeply localized levels only quasiparticle cotunneling is observed, for slightly delocalized levels Shiba bound states form and a parity-changing quantum phase transition is identified by a crossing of the bound states at zero energy. Finally, in the metallic regime, single Andreev resonances are observed.
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Affiliation(s)
- Alexandre Assouline
- LPEM, ESPCI Paris, PSL Research University; CNRS; Sorbonne Universités, UPMC University of Paris 6, 10 rue Vauquelin, F-75005 Paris, France
| | - Cheryl Feuillet-Palma
- LPEM, ESPCI Paris, PSL Research University; CNRS; Sorbonne Universités, UPMC University of Paris 6, 10 rue Vauquelin, F-75005 Paris, France
| | - Alexandre Zimmers
- LPEM, ESPCI Paris, PSL Research University; CNRS; Sorbonne Universités, UPMC University of Paris 6, 10 rue Vauquelin, F-75005 Paris, France
| | - Hervé Aubin
- LPEM, ESPCI Paris, PSL Research University; CNRS; Sorbonne Universités, UPMC University of Paris 6, 10 rue Vauquelin, F-75005 Paris, France
| | - Marco Aprili
- Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, University Paris-Saclay, 91405 Orsay Cedex, France
| | - Jean-Christophe Harmand
- Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Sud, Universités Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
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16
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Winkler GW, Varjas D, Skolasinski R, Soluyanov AA, Troyer M, Wimmer M. Orbital Contributions to the Electron g Factor in Semiconductor Nanowires. PHYSICAL REVIEW LETTERS 2017; 119:037701. [PMID: 28777644 DOI: 10.1103/physrevlett.119.037701] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Indexed: 06/07/2023]
Abstract
Recent experiments on Majorana fermions in semiconductor nanowires [S. M. Albrecht, A. P. Higginbotham, M. Madsen, F. Kuemmeth, T. S. Jespersen, J. Nygård, P. Krogstrup, and C. M. Marcus, Nature (London) 531, 206 (2016)NATUAS0028-083610.1038/nature17162] revealed a surprisingly large electronic Landé g factor, several times larger than the bulk value-contrary to the expectation that confinement reduces the g factor. Here we assess the role of orbital contributions to the electron g factor in nanowires and quantum dots. We show that an L·S coupling in higher subbands leads to an enhancement of the g factor of an order of magnitude or more for small effective mass semiconductors. We validate our theoretical finding with simulations of InAs and InSb, showing that the effect persists even if cylindrical symmetry is broken. A huge anisotropy of the enhanced g factors under magnetic field rotation allows for a straightforward experimental test of this theory.
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Affiliation(s)
- Georg W Winkler
- Theoretical Physics and Station Q Zurich, ETH Zurich, 8093 Zurich, Switzerland
| | - Dániel Varjas
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Rafal Skolasinski
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Alexey A Soluyanov
- Theoretical Physics and Station Q Zurich, ETH Zurich, 8093 Zurich, Switzerland
- Department of Physics, Saint Petersburg State University, Saint Petersburg 199034, Russia
| | - Matthias Troyer
- Theoretical Physics and Station Q Zurich, ETH Zurich, 8093 Zurich, Switzerland
- Quantum Architectures and Computation Group, Microsoft Research, Redmond, Washington 98052, USA
| | - Michael Wimmer
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
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17
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Wang JY, Huang S, Huang GY, Pan D, Zhao J, Xu HQ. Coherent Transport in a Linear Triple Quantum Dot Made from a Pure-Phase InAs Nanowire. NANO LETTERS 2017; 17:4158-4164. [PMID: 28604002 DOI: 10.1021/acs.nanolett.7b00927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A highly tunable linear triple quantum dot (TQD) device is realized in a single-crystalline pure-phase InAs nanowire using a local finger gate technique. The electrical measurements show that the charge stability diagram of the TQD can be represented by three kinds of current lines of different slopes and a simulation performed based on a capacitance matrix model confirms the experiment. We show that each current line observable in the charge stability diagram is associated with a case where a QD is on resonance with the Fermi level of the source and drain reservoirs. At a triple point where two current lines of different slopes move together but show anticrossing, two QDs are on resonance with the Fermi level of the reservoirs. We demonstrate that an energetically degenerated quadruple point at which all three QDs are on resonance with the Fermi level of the reservoirs can be built by moving two separated triple points together via sophistically tuning of energy levels in the three QDs. We also demonstrate the achievement of direct coherent electron transfer between the two remote QDs in the TQD, realizing a long-distance coherent quantum bus operation. Such a long-distance coherent coupling could be used to investigate coherent spin teleportation and superexchange effects and to construct a spin qubit with an improved long coherent time and with spin state detection solely by sensing the charge states.
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Affiliation(s)
- Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University , Beijing 100871, China
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University , Beijing 100871, China
| | - Guang-Yao Huang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University , Beijing 100871, China
| | - Dong Pan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences , Beijing 100083, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences , Beijing 100083, China
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and Department of Electronics, Peking University , Beijing 100871, China
- Division of Solid State Physics, Lund University , Box 118, S-22100 Lund, Sweden
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18
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Albrecht SM, Hansen EB, Higginbotham AP, Kuemmeth F, Jespersen TS, Nygård J, Krogstrup P, Danon J, Flensberg K, Marcus CM. Transport Signatures of Quasiparticle Poisoning in a Majorana Island. PHYSICAL REVIEW LETTERS 2017; 118:137701. [PMID: 28409973 DOI: 10.1103/physrevlett.118.137701] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Indexed: 06/07/2023]
Abstract
We investigate effects of quasiparticle poisoning in a Majorana island with strong tunnel coupling to normal-metal leads. In addition to the main Coulomb blockade diamonds, "shadow" diamonds appear, shifted by 1e in gate voltage, consistent with transport through an excited (poisoned) state of the island. Comparison to a simple model yields an estimate of parity lifetime for the strongly coupled island (∼1 μs) and sets a bound for a weakly coupled island (>10 μs). Fluctuations in the gate-voltage spacing of Coulomb peaks at high field, reflecting Majorana hybridization, are enhanced by the reduced lever arm at strong coupling. When converted from gate voltage to energy units, fluctuations are consistent with previous measurements.
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Affiliation(s)
- S M Albrecht
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - E B Hansen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - A P Higginbotham
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
- JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - F Kuemmeth
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - T S Jespersen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - J Nygård
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - P Krogstrup
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - J Danon
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
- Department of Physics, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - K Flensberg
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - C M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
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19
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Chen IJ, Lehmann S, Nilsson M, Kivisaari P, Linke H, Dick KA, Thelander C. Conduction Band Offset and Polarization Effects in InAs Nanowire Polytype Junctions. NANO LETTERS 2017; 17:902-908. [PMID: 28002673 DOI: 10.1021/acs.nanolett.6b04211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Although zinc-blende (ZB) and wurtzite (WZ) structures differ only in the atomic stacking sequence, mixing of crystal phases can strongly affect the electronic properties, a problem particularly common to bottom up-grown nanostructures. A lack of understanding of the nature of electronic transport at crystal phase junctions thus severely limits our ability to develop functional nanowire devices. In this work we investigated electron transport in InAs nanowires with designed mixing of crystal structures, ZB/WZ/ZB, by temperature-dependent electrical measurements. The WZ inclusion gives rise to an energy barrier in the conduction band. Interpreting the experimental result in terms of thermionic emission and using a drift-diffusion model, we extracted values for the WZ/ZB band offset, 135 ± 10 meV, and interface sheet polarization charge density on the order of 10-3 C/m2. The extracted polarization charge density is 1-2 orders of magnitude smaller than previous experimental results, but in good agreement with first principle calculation of spontaneous polarization in WZ InAs. When the WZ length is reduced below 20 nm, an effective barrier lowering is observed, indicating the increasing importance of tunneling transport. Finally, we found that band-bending at ZB/WZ junctions can lead to bound electron states within an enclosed WZ segment of sufficient length, evidenced by our observation of Coulomb blockade at low temperature. These findings provide critical input for modeling and designing the electronic properties of novel functional devices, such as nanowire transistors, where crystal polytypes are commonly found.
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Affiliation(s)
- I-Ju Chen
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Sebastian Lehmann
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Malin Nilsson
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Pyry Kivisaari
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Heiner Linke
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Kimberly A Dick
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
| | - Claes Thelander
- Solid State Physics and NanoLund and ‡Center for Analysis and Synthesis, Lund University , S-221 00 Lund, Sweden
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20
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Heedt S, Prost W, Schubert J, Grützmacher D, Schäpers T. Ballistic Transport and Exchange Interaction in InAs Nanowire Quantum Point Contacts. NANO LETTERS 2016; 16:3116-3123. [PMID: 27104768 DOI: 10.1021/acs.nanolett.6b00414] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
One-dimensional ballistic transport is demonstrated for a high-mobility InAs nanowire device. Unlike conventional quantum point contacts (QPCs) created in a two-dimensional electron gas, the nanowire QPCs represent one-dimensional constrictions formed inside a quasi-one-dimensional conductor. For each QPC, the local subband occupation can be controlled individually between zero and up to six degenerate modes. At large out-of-plane magnetic fields Landau quantization and Zeeman splitting emerge and comprehensive voltage bias spectroscopy is performed. Confinement-induced quenching of the orbital motion gives rise to significantly modified subband-dependent Landé g factors. A pronounced g factor enhancement related to Coulomb exchange interaction is reported. Many-body effects of that kind also manifest in the observation of the 0.7·2e(2)/h conductance anomaly, commonly found in planar devices.
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Affiliation(s)
- S Heedt
- Peter Grünberg Institut (PGI-9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - W Prost
- Solid State Electronics Department, University of Duisburg-Essen , 47057 Duisburg, Germany
| | - J Schubert
- Peter Grünberg Institut (PGI-9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - D Grützmacher
- Peter Grünberg Institut (PGI-9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Th Schäpers
- Peter Grünberg Institut (PGI-9) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich , 52425 Jülich, Germany
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21
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Albrecht SM, Higginbotham AP, Madsen M, Kuemmeth F, Jespersen TS, Nygård J, Krogstrup P, Marcus CM. Exponential protection of zero modes in Majorana islands. Nature 2016; 531:206-9. [DOI: 10.1038/nature17162] [Citation(s) in RCA: 770] [Impact Index Per Article: 96.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 01/18/2016] [Indexed: 11/09/2022]
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22
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Fülöp G, Domínguez F, d'Hollosy S, Baumgartner A, Makk P, Madsen MH, Guzenko VA, Nygård J, Schönenberger C, Levy Yeyati A, Csonka S. Magnetic Field Tuning and Quantum Interference in a Cooper Pair Splitter. PHYSICAL REVIEW LETTERS 2015; 115:227003. [PMID: 26650317 DOI: 10.1103/physrevlett.115.227003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Indexed: 06/05/2023]
Abstract
Cooper pair splitting (CPS) is a process in which the electrons of the naturally occurring spin-singlet pairs in a superconductor are spatially separated using two quantum dots. Here, we investigate the evolution of the conductance correlations in an InAs CPS device in the presence of an external magnetic field. In our experiments the gate dependence of the signal that depends on both quantum dots continuously evolves from a slightly asymmetric Lorentzian to a strongly asymmetric Fano-type resonance with increasing field. These experiments can be understood in a simple three-site model, which shows that the nonlocal CPS leads to symmetric line shapes, while the local transport processes can exhibit an asymmetric shape due to quantum interference. These findings demonstrate that the electrons from a Cooper pair splitter can propagate coherently after their emission from the superconductor and how a magnetic field can be used to optimize the performance of a CPS device. In addition, the model calculations suggest that the estimate of the CPS efficiency in the experiments is a lower bound for the actual efficiency.
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Affiliation(s)
- G Fülöp
- Department of Physics, Budapest University of Technology and Economics, and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budafoki út 8, 1111 Budapest, Hungary
| | - F Domínguez
- Departamento de Física Teórica de la Materia Condensada, Condensed Matter Physics Center (IFIMAC), and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - S d'Hollosy
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - A Baumgartner
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - P Makk
- Department of Physics, Budapest University of Technology and Economics, and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budafoki út 8, 1111 Budapest, Hungary
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - M H Madsen
- Center for Quantum Devices & Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - V A Guzenko
- Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - J Nygård
- Center for Quantum Devices & Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - C Schönenberger
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - A Levy Yeyati
- Departamento de Física Teórica de la Materia Condensada, Condensed Matter Physics Center (IFIMAC), and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - S Csonka
- Department of Physics, Budapest University of Technology and Economics, and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budafoki út 8, 1111 Budapest, Hungary
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23
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Fan D, Li S, Kang N, Caroff P, Wang LB, Huang YQ, Deng MT, Yu CL, Xu HQ. Formation of long single quantum dots in high quality InSb nanowires grown by molecular beam epitaxy. NANOSCALE 2015; 7:14822-14828. [PMID: 26308470 DOI: 10.1039/c5nr04273a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO2 substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ∼700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Landég-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ∼300 μeV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.
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Affiliation(s)
- Dingxun Fan
- Department of Electronics and Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing 100871, China.
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24
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Rainis D, Saha A, Klinovaja J, Trifunovic L, Loss D. Transport signatures of fractional fermions in Rashba nanowires. PHYSICAL REVIEW LETTERS 2014; 112:196803. [PMID: 24877960 DOI: 10.1103/physrevlett.112.196803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Indexed: 06/03/2023]
Abstract
We theoretically study transport through a semiconducting Rashba nanowire (NW) in the presence of uniform and spatially modulated magnetic fields. The system is fully gapped, and the interplay between the spin orbit interaction and the magnetic fields leads to fractionally charged fermion (FF) bound states of the Jackiw-Rebbi type at each end of the nanowire. We investigate the transport and noise behavior of a N/NW/N system, where the wire is contacted by two normal leads (N), and we look for possible signatures that could help in the experimental detection of such states. We find that the differential conductance and the shot noise exhibit a subgap structure which fully reveals the presence of the FF state. Alternatively, another confirmation of the presence of the FFs is provided by a conductance measurement in an Aharonov-Bohm setup, where the FFs are responsible for oscillations with double period. Our predictions can be tested in InSb/InAs nanowires and are within reach of the present technology.
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Affiliation(s)
- Diego Rainis
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Arijit Saha
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Jelena Klinovaja
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Luka Trifunovic
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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25
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van Bree J, Silov AY, Koenraad PM, Flatté ME. Spin-orbit-induced circulating currents in a semiconductor nanostructure. PHYSICAL REVIEW LETTERS 2014; 112:187201. [PMID: 24856716 DOI: 10.1103/physrevlett.112.187201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Indexed: 06/03/2023]
Abstract
Circulating orbital currents produced by the spin-orbit interaction for a single electron spin in a quantum dot are explicitly evaluated at zero magnetic field, along with their effect on the total magnetic moment (spin and orbital) of the electron spin. The currents are dominated by coherent superpositions of the conduction and valence envelope functions of the electronic state, are smoothly varying within the quantum dot, and are peaked roughly halfway between the dot center and edge. Thus the spatial structure of the spin contribution to the magnetic moment (which is peaked at the dot center) differs greatly from the spatial structure of the orbital contribution. Even when the spin and orbital magnetic moments cancel (for g=0) the spin can interact strongly with local magnetic fields, e.g., from other spins, which has implications for spin lifetimes and spin manipulation.
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Affiliation(s)
- J van Bree
- PSN, COBRA Research Institute, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - A Yu Silov
- PSN, COBRA Research Institute, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - P M Koenraad
- PSN, COBRA Research Institute, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - M E Flatté
- PSN, COBRA Research Institute, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands and Department of Physics and Astronomy and Optical Science and Technology Center, University of Iowa, Iowa City, Iowa 52242, USA
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26
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Vigneau F, Prudkovkiy V, Duchemin I, Escoffier W, Caroff P, Niquet YM, Leturcq R, Goiran M, Raquet B. Magnetotransport subband spectroscopy in InAs nanowires. PHYSICAL REVIEW LETTERS 2014; 112:076801. [PMID: 24579622 DOI: 10.1103/physrevlett.112.076801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Indexed: 06/03/2023]
Abstract
We report on magnetotransport measurements in InAs nanowires under a large magnetic field (up to 55 T), providing a spectroscopy of the one-dimensional electronic band structure. Large modulations of the conductance mediated by a control of the Fermi energy reveal the Landau fragmentation, carrying the fingerprints of the confined InAs material. Our numerical simulations of the magnetic band structure consistently support the experimental results and reveal key parameters of the electronic confinement.
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Affiliation(s)
- Florian Vigneau
- Laboratoire National des Champs Magnétiques Intenses, INSA UPS UJF CNRS, UPR 3228, Université de Toulouse, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - Vladimir Prudkovkiy
- Laboratoire National des Champs Magnétiques Intenses, INSA UPS UJF CNRS, UPR 3228, Université de Toulouse, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - Ivan Duchemin
- L-Sim, SP2M, UMR-E CEA/UJF-Grenoble 1, INAC, 17 Rue des Martyrs, 38054 Grenoble, France
| | - Walter Escoffier
- Laboratoire National des Champs Magnétiques Intenses, INSA UPS UJF CNRS, UPR 3228, Université de Toulouse, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - Philippe Caroff
- Institute of Electronics Microelectronics and Nanotechnology, CNRS-UMR 8520, ISEN Department, Avenue Poincaré, CS 60069, 59652 Villeneuve d'Ascq Cedex, France and Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, Australian Capital Territory 0200, Australia
| | - Yann-Michel Niquet
- L-Sim, SP2M, UMR-E CEA/UJF-Grenoble 1, INAC, 17 Rue des Martyrs, 38054 Grenoble, France
| | - Renaud Leturcq
- Institute of Electronics Microelectronics and Nanotechnology, CNRS-UMR 8520, ISEN Department, Avenue Poincaré, CS 60069, 59652 Villeneuve d'Ascq Cedex, France
| | - Michel Goiran
- Laboratoire National des Champs Magnétiques Intenses, INSA UPS UJF CNRS, UPR 3228, Université de Toulouse, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - Bertrand Raquet
- Laboratoire National des Champs Magnétiques Intenses, INSA UPS UJF CNRS, UPR 3228, Université de Toulouse, 143 Avenue de Rangueil, 31400 Toulouse, France
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27
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Finck ADK, Van Harlingen DJ, Mohseni PK, Jung K, Li X. Anomalous modulation of a zero-bias peak in a hybrid nanowire-superconductor device. PHYSICAL REVIEW LETTERS 2013; 110:126406. [PMID: 25166828 DOI: 10.1103/physrevlett.110.126406] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Indexed: 05/22/2023]
Abstract
We report on transport measurements of an InAs nanowire coupled to niobium nitride leads at high magnetic fields. We observe a zero-bias anomaly (ZBA) in the differential conductance of the nanowire for certain ranges of magnetic field and chemical potential. The ZBA can oscillate in width with either the magnetic field or chemical potential; it can even split and re-form. We discuss how our results relate to recent predictions of hybridizing Majorana fermions in semiconducting nanowires, while considering more mundane explanations.
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Affiliation(s)
- A D K Finck
- Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - D J Van Harlingen
- Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - P K Mohseni
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - K Jung
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - X Li
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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28
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van Weperen I, Plissard SR, Bakkers EPAM, Frolov SM, Kouwenhoven LP. Quantized conductance in an InSb nanowire. NANO LETTERS 2013; 13:387-391. [PMID: 23259576 DOI: 10.1021/nl3035256] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Ballistic one-dimensional transport in semiconductor nanowires plays a central role in creating topological and helical states. The hallmark of such one-dimensional transport is conductance quantization. Here we show conductance quantization in InSb nanowires at nonzero magnetic fields. Conductance plateaus are studied as a function of source-drain bias and magnetic field, enabling extraction of the Landé g factor and the subband spacing.
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Affiliation(s)
- Ilse van Weperen
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
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29
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Sourribes MJL, Isakov I, Panfilova M, Warburton PA. Minimization of the contact resistance between InAs nanowires and metallic contacts. NANOTECHNOLOGY 2013; 24:045703. [PMID: 23299854 DOI: 10.1088/0957-4484/24/4/045703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate different processes for optimizing the formation of Ohmic contacts to InAs nanowires. The nanowires are grown via molecular beam epitaxy without the use of metal catalysts. Metallic contacts are attached to the nanowires by using an electron beam lithography process. Before deposition of the contacts, the InAs nanowires are treated either by wet etching in an ammonium polysulfide (NH(4))(2)S(x) solution or by an argon milling process in order to remove a surface oxide layer. Two-point electrical measurements show that the resistance of the ammonium polysulfide-treated nanowires is two orders of magnitude lower than that of the untreated nanowires. The nanowires that are treated by the argon milling process show a resistance which is more than an order of magnitude lower than that of those treated with ammonium polysulfide. Four-point measurements allow us to extract an upper bound of 1.4 × 10(-7) Ω cm(2) for the contact resistivity of metallic contacts on nanowires treated by the argon milling process.
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Affiliation(s)
- M J L Sourribes
- London Centre for Nanotechnology, University College London, Gower Street, London WC1H 0AH, UK.
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30
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Abstract
The light-hole g value in Al x Ga 1-x As is found to show scaling behavior as a function of quantum well width, g ≃( well width )-β with β ≃ 0.3. When x is varied to change the Ga concentration there is a critical value of the concentration of 1 - x0 = 0.88, at which the g value vanishes, g⊥ = 0. There is a scaling behavior, g⊥ = 2[1 - (1 - x)/(1 - xo)]y. The g⊥ data varies from about -0.42 for x = 0 to 0.60 for x = 0.374. Hence, the large variations in the g values are due to a phase transition. Similar results for InAs are also discussed. The contribution to the g value arising from the Calogero-type potential is deduced, which gives rise to wave functions in the form of Jack polynomials.
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Affiliation(s)
- KESHAV N. SHRIVASTAVA
- School of Physics, University of Hyderabad, Hyderabad 500046, India
- Department of Physics, University of Malaya, Kuala Lumpur 50603, Malaysia
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31
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Schroer MD, Petersson KD, Jung M, Petta JR. Field tuning the g factor in InAs nanowire double quantum dots. PHYSICAL REVIEW LETTERS 2011; 107:176811. [PMID: 22107563 DOI: 10.1103/physrevlett.107.176811] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2011] [Indexed: 05/31/2023]
Abstract
We study the effects of magnetic and electric fields on the g factors of spins confined in a two-electron InAs nanowire double quantum dot. Spin sensitive measurements are performed by monitoring the leakage current in the Pauli blockade regime. Rotations of single spins are driven using electric-dipole spin resonance. The g factors are extracted from the spin resonance condition as a function of the magnetic field direction, allowing determination of the full g tensor. Electric and magnetic field tuning can be used to maximize the g-factor difference and in some cases altogether quench the electric-dipole spin resonance response, allowing selective single spin control.
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Affiliation(s)
- M D Schroer
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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32
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Hofstetter L, Csonka S, Baumgartner A, Fülöp G, d'Hollosy S, Nygård J, Schönenberger C. Finite-bias Cooper pair splitting. PHYSICAL REVIEW LETTERS 2011; 107:136801. [PMID: 22026885 DOI: 10.1103/physrevlett.107.136801] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Indexed: 05/31/2023]
Abstract
In a device with a superconductor coupled to two parallel quantum dots (QDs) the electrical tunability of the QD levels can be used to exploit nonclassical current correlations due to the splitting of Cooper pairs. We experimentally investigate the effect of a finite potential difference across one quantum dot on the conductance through the other completely grounded QD in a Cooper pair splitter fabricated on an InAs nanowire. We demonstrate that the nonlocal electrical transport through the device can be tuned by electrical means and that the energy dependence of the effective density of states in the QDs is relevant for the rates of Cooper pair splitting (CPS) and elastic cotunneling. Such experimental tools are necessary to understand and develop CPS-based sources of entangled electrons in solid-state devices.
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Affiliation(s)
- L Hofstetter
- Department of Physics, University of Basel, Switzerland
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33
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Kanai Y, Deacon RS, Takahashi S, Oiwa A, Yoshida K, Shibata K, Hirakawa K, Tokura Y, Tarucha S. Electrically tuned spin-orbit interaction in an InAs self-assembled quantum dot. NATURE NANOTECHNOLOGY 2011; 6:511-516. [PMID: 21785428 DOI: 10.1038/nnano.2011.103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 06/02/2011] [Indexed: 05/31/2023]
Abstract
Electrical control over electron spin is a prerequisite for spintronics spin-based quantum information processing. In particular, control over the interaction between the orbital motion and the spin state of electrons would be valuable, because this interaction influences spin relaxation and dephasing. Electric fields have been used to tune the strength of the spin-orbit interaction in two-dimensional electron gases, but not, so far, in quantum dots. Here, we demonstrate that electrical gating can be used to vary the energy of the spin-orbit interaction in the range 50-150 µeV while maintaining the electron occupation of a single self-assembled InAs quantum dot. We determine the spin-orbit interaction energy by observing the splitting of Kondo effect features at high magnetic fields.
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Affiliation(s)
- Y Kanai
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656, Japan
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34
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Liu G, Chen Y, Jia C, Hao GD, Wang Z. Spin splitting modulated by uniaxial stress in InAs nanowires. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:015801. [PMID: 21406826 DOI: 10.1088/0953-8984/23/1/015801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We theoretically study the electronic structure, spin splitting, effective mass, and spin orientation of InAs nanowires with cylindrical symmetry in the presence of an external electric field and uniaxial stress. Using an eight-band k·p theoretical model, we deduce a formula for the spin splitting in the system, indicating that the spin splitting under uniaxial stress is a nonlinear function of the momentum and the electric field. The spin splitting can be described by a linear Rashba model when the wavevector and the electric field are sufficiently small. Our numeric results show that the uniaxial stress can modulate the spin splitting. With the increase of wavevector, the uniaxial tensile stress first restrains and then amplifies the spin splitting of the lowest electron state compared to the no strain case. The reverse is true under a compression. Moreover, strong spin splitting can be induced by compression when the top of the valence band is close to the bottom of the conductance band, and the spin orientations of the electron stay almost unchanged before the overlap of the two bands.
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Affiliation(s)
- Genhua Liu
- Key Laboratory of Semiconductor Material Science, Institute of Semiconductors, Chinese Academy of Science, PO Box 912, Beijing 100083, People's Republic of China
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35
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Kretinin AV, Popovitz-Biro R, Mahalu D, Shtrikman H. Multimode Fabry-Perot conductance oscillations in suspended stacking-faults-free InAs nanowires. NANO LETTERS 2010; 10:3439-3445. [PMID: 20695446 DOI: 10.1021/nl101522j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report on observation of coherent electron transport in suspended high-quality InAs nanowire-based devices. The InAs nanowires were grown by low-temperature gold-assisted vapor-liquid-solid molecular-beam-epitaxy. The high quality of the nanowires was achieved by removing the typically found stacking faults and reducing possibility of Au incorporation. Minimizing substrate-induced scattering in the device was achieved by suspending the nanowires over predefined grooves. Coherent transport involving more than a single one-dimensional mode transport was observed in the experiment and manifested by Fabry-Perot conductance oscillations. The length of the Fabry-Perot interferometer, deduced from the period of the conductance oscillations, was found to be close to the physical length of the device. The high oscillations visibility imply nearly ballistic electron transport through the nanowire.
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Affiliation(s)
- Andrey V Kretinin
- Department of Condensed Matter Physics, Weizmann Institute of Science, Braun Center for Submicrometer Research, Israel.
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36
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Hofstetter L, Geresdi A, Aagesen M, Nygård J, Schönenberger C, Csonka S. Ferromagnetic proximity effect in a ferromagnet-quantum-dot-superconductor device. PHYSICAL REVIEW LETTERS 2010; 104:246804. [PMID: 20867324 DOI: 10.1103/physrevlett.104.246804] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Indexed: 05/29/2023]
Abstract
The ferromagnetic proximity effect is studied in InAs nanowire based quantum dots strongly coupled to a ferromagnetic (F) and a superconducting (S) lead. The influence of the F lead is detected through the splitting of the spin-1/2 Kondo resonance. We show that the F lead induces a local exchange field on the quantum dot, which has varying amplitude and sign depending on the charge states. The interplay of the F and S correlations generates an exchange field related subgap feature.
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Affiliation(s)
- L Hofstetter
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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37
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Katsaros G, Spathis P, Stoffel M, Fournel F, Mongillo M, Bouchiat V, Lefloch F, Rastelli A, Schmidt OG, De Franceschi S. Hybrid superconductor-semiconductor devices made from self-assembled SiGe nanocrystals on silicon. NATURE NANOTECHNOLOGY 2010; 5:458-464. [PMID: 20436467 DOI: 10.1038/nnano.2010.84] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 03/25/2010] [Indexed: 05/27/2023]
Abstract
The epitaxial growth of germanium on silicon leads to the self-assembly of SiGe nanocrystals by a process that allows the size, composition and position of the nanocrystals to be controlled. This level of control, combined with an inherent compatibility with silicon technology, could prove useful in nanoelectronic applications. Here, we report the confinement of holes in quantum-dot devices made by directly contacting individual SiGe nanocrystals with aluminium electrodes, and the production of hybrid superconductor-semiconductor devices, such as resonant supercurrent transistors, when the quantum dot is strongly coupled to the electrodes. Charge transport measurements on weakly coupled quantum dots reveal discrete energy spectra, with the confined hole states displaying anisotropic gyromagnetic factors and strong spin-orbit coupling with pronounced dependences on gate voltage and magnetic field.
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Affiliation(s)
- G Katsaros
- CEA, INAC/SPSMS/LaTEQS, 17 Rue des Martyrs, 38054 Grenoble, France.
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38
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Cooper pair splitter realized in a two-quantum-dot Y-junction. Nature 2009; 461:960-3. [DOI: 10.1038/nature08432] [Citation(s) in RCA: 383] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 08/18/2009] [Indexed: 11/08/2022]
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39
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Nilsson HA, Caroff P, Thelander C, Larsson M, Wagner JB, Wernersson LE, Samuelson L, Xu HQ. Giant, level-dependent g factors in InSb nanowire quantum dots. NANO LETTERS 2009; 9:3151-3156. [PMID: 19736971 DOI: 10.1021/nl901333a] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report on magnetotransport measurements on InSb nanowire quantum dots. The measurements show that the quantum levels of the InSb quantum dots have giant g factors, with absolute values up to approximately 70, the largest value ever reported for semiconductor quantum dots. We also observe that the values of these g factors are quantum level dependent and can differ strongly between different quantum levels. The presence of giant g factors indicates that considerable contributions from the orbital motion of electrons are preserved in the measured InSb nanowire quantum dots, while the level-to-level fluctuations arise from spin-orbit interaction. We have deduced a value of Delta(SO) = 280 mueV for the strength of spin-orbit interaction from an avoided level crossing between the ground state and first excited state of an InSb nanowire quantum dot with a fixed number of electrons.
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Affiliation(s)
- Henrik A Nilsson
- Division of Solid State Physics, Lund University, S-22100 Lund, Sweden
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