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Denisov AO, Oh SW, Fuchs G, Mills AR, Chen P, Anderson CR, Gyure MF, Barnard AW, Petta JR. Microwave-Frequency Scanning Gate Microscopy of a Si/SiGe Double Quantum Dot. NANO LETTERS 2022; 22:4807-4813. [PMID: 35678453 DOI: 10.1021/acs.nanolett.2c01098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Conventional transport methods provide quantitative information on spin, orbital, and valley states in quantum dots but lack spatial resolution. Scanning tunneling microscopy, on the other hand, provides exquisite spatial resolution at the expense of speed. Working to combine the spatial resolution and energy sensitivity of scanning probe microscopy with the speed of microwave measurements, we couple a metallic tip to a Si/SiGe double quantum dot (DQD) that is integrated with a charge detector. We first demonstrate that the dc-biased tip can be used to change the occupancy of the DQD. We then apply microwaves through the tip to drive photon-assisted tunneling (PAT). We infer the DQD level diagram from the frequency and detuning dependence of the tunneling resonances. These measurements allow the resolution of ∼65 μeV excited states, an energy consistent with valley splittings in Si/SiGe. This work demonstrates the feasibility of scanning gate experiments with Si/SiGe devices.
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Affiliation(s)
- Artem O Denisov
- Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
| | - Seong W Oh
- Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
| | - Gordian Fuchs
- Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
| | - Adam R Mills
- Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
| | - Pengcheng Chen
- Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, United States
| | - Christopher R Anderson
- Department of Mathematics, University of California, Los Angeles, California 90095, United States
| | - Mark F Gyure
- Center for Quantum Science and Engineering, University of California, Los Angeles, California 90095, United States
| | - Arthur W Barnard
- Department of Physics, University of Washington, 98195 Seattle, Washington United States
- Department of Materials Science and Engineering, University of Washington, 98195 Seattle, Washington United States
| | - Jason R Petta
- Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
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2
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Martin Lanzoni E, Covre da Silva SF, Knopper MF, Garcia AJ, Costa CAR, Deneke C. Imaging the electrostatic landscape of unstrained self-assemble GaAs quantum dots. NANOTECHNOLOGY 2022; 33:165701. [PMID: 34983039 DOI: 10.1088/1361-6528/ac47ce] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 01/03/2022] [Indexed: 06/14/2023]
Abstract
Unstrained GaAs quantum dots are promising candidates for quantum information devices due to their optical properties, but their electronic properties have remained relatively unexplored until now. In this work, we systematically investigate the electronic structure and natural charging of GaAs quantum dots at room temperature using Kelvin probe force microscopy (KPFM). We observe a clear electrical signal from these structures demonstrating a lower surface potential in the middle of the dot. We ascribe this to charge accumulation and confinement inside these structures. Our systematical investigation reveals that the change in surface potential is larger for a nominal dot filling of 2 nm and then starts to decrease for thicker GaAs layers. Usingk·pcalculation, we show that the confinement comes from the band bending due to the surface Fermi level pinning. We find a correlation between the calculated charge density and the KPFM signal indicating thatk·pcalculations could be used to estimate the KPFM signal for a given structure. Our results suggest that these self-assembled structures could be used to study physical phenomena connected to charged quantum dots like Coulomb blockade or Kondo effect.
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Affiliation(s)
- Evandro Martin Lanzoni
- São Paulo State University (UNESP), Institute of Science and Technology, 18087-180 Sorocaba, Brazil
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970 Campinas, Brazil
- University of Luxembourg, Physics and Materials Science Research Unit, 1511 Luxembourg, Luxembourg
| | - Saimon F Covre da Silva
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970 Campinas, Brazil
- Universidade Federal de Viçosa (UFV), Departamento de Física, 36570-000 Viçosa, Brasil
| | - Matthijn Floris Knopper
- Eindhoven University of Technology (TU/e), Department of Applied Physics, 5600 Eindhoven,The Netherland
| | - Ailton J Garcia
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970 Campinas, Brazil
- Universidade Estadual de Campinas, Instituto de Física 'Gleb Wataghin', 13083-859 Campinas, Brazil
| | - Carlos Alberto Rodrigues Costa
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970 Campinas, Brazil
| | - Christoph Deneke
- Universidade Estadual de Campinas, Instituto de Física 'Gleb Wataghin', 13083-859 Campinas, Brazil
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3
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Brun B, Nguyen VH, Moreau N, Somanchi S, Watanabe K, Taniguchi T, Charlier JC, Stampfer C, Hackens B. Graphene Whisperitronics: Transducing Whispering Gallery Modes into Electronic Transport. NANO LETTERS 2022; 22:128-134. [PMID: 34898223 DOI: 10.1021/acs.nanolett.1c03451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
When confined in circular cavities, graphene relativistic charge carriers occupy whispering gallery modes (WGMs) in analogy to classical acoustic and optical fields. The rich geometrical patterns of the WGMs decorating the local density of states offer promising perspectives to devise new disruptive quantum devices. However, exploiting these highly sensitive resonances requires the transduction of the WGMs to the outside world through source and drain electrodes, a yet unreported configuration. Here, we create a circular p-n island in a graphene device using a polarized scanning gate microscope tip and probe the resulting WGM signatures in in-plane electronic transport through the p-n island. Combining tight-binding simulations and the exact solution of the Dirac equation, we assign the measured device conductance features to WGMs and demonstrate mode selectivity by displacing the p-n island with respect to a constriction. This work therefore constitutes a proof of concept for graphene whisperitronic devices.
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Affiliation(s)
- Boris Brun
- IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve, Belgium
| | - Viet-Hung Nguyen
- IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve, Belgium
| | - Nicolas Moreau
- IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve, Belgium
| | - Sowmya Somanchi
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52062 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - 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
| | - Jean-Christophe Charlier
- IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve, Belgium
| | - Christoph Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52062 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Benoit Hackens
- IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve, Belgium
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4
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Moreau N, Brun B, Somanchi S, Watanabe K, Taniguchi T, Stampfer C, Hackens B. Upstream modes and antidots poison graphene quantum Hall effect. Nat Commun 2021; 12:4265. [PMID: 34253725 PMCID: PMC8275581 DOI: 10.1038/s41467-021-24481-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 06/17/2021] [Indexed: 11/09/2022] Open
Abstract
The quantum Hall effect is the seminal example of topological protection, as charge carriers are transmitted through one-dimensional edge channels where backscattering is prohibited. Graphene has made its marks as an exceptional platform to reveal new facets of this remarkable property. However, in conventional Hall bar geometries, topological protection of graphene edge channels is found regrettably less robust than in high mobility semi-conductors. Here, we explore graphene quantum Hall regime at the local scale, using a scanning gate microscope. We reveal the detrimental influence of antidots along the graphene edges, mediating backscattering towards upstream edge channels, hence triggering topological breakdown. Combined with simulations, our experimental results provide further insights into graphene quantum Hall channels vulnerability. In turn, this may ease future developments towards precise manipulation of topologically protected edge channels hosted in various types of two-dimensional crystals.
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Affiliation(s)
- N Moreau
- IMCN/NAPS, Université catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium
| | - B Brun
- IMCN/NAPS, Université catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium
| | - S Somanchi
- JARA-FIT and 2nd Institute of Physics-RWTH Aachen, Aachen, Germany
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics-RWTH Aachen, Aachen, Germany
| | - B Hackens
- IMCN/NAPS, Université catholique de Louvain (UCLouvain), Louvain-la-Neuve, Belgium.
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5
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Bhandari S, Lee GH, Watanabe K, Taniguchi T, Kim P, Westervelt RM. Imaging Andreev Reflection in Graphene. NANO LETTERS 2020; 20:4890-4894. [PMID: 32484357 DOI: 10.1021/acs.nanolett.0c00903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Coherent charge transport along ballistic paths can be introduced into graphene by Andreev reflection, for which an electron reflects from a superconducting contact as a hole, while a Cooper pair is transmitted. We use liquid-helium cooled scanning gate microscopy (SGM) to image Andreev reflection in graphene in the magnetic focusing regime, where carriers move along cyclotron orbits between contacts. Images of flow are obtained by deflecting carrier paths and displaying the resulting change in conductance. When electrons enter the superconductor, Andreev-reflected holes leave for the collecting contact. To test the results, we destroy Andreev reflection with a large current and by heating above the critical temperature. In both cases, the reflected carriers change from holes to electrons.
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Affiliation(s)
- Sagar Bhandari
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Physics and Engineering, Slippery Rock University, Slippery Rock, Pennsylvania 16057, United States
| | - Gil-Ho Lee
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
| | - 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
| | - Philip Kim
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Robert M Westervelt
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
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6
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Camenzind LC, Yu L, Stano P, Zimmerman JD, Gossard AC, Loss D, Zumbühl DM. Spectroscopy of Quantum Dot Orbitals with In-Plane Magnetic Fields. PHYSICAL REVIEW LETTERS 2019; 122:207701. [PMID: 31172765 DOI: 10.1103/physrevlett.122.207701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 02/05/2019] [Indexed: 06/09/2023]
Abstract
We show that in-plane magnetic-field-assisted spectroscopy allows extraction of the in-plane orientation and full 3D size parameters of the quantum mechanical orbitals of a single electron GaAs lateral quantum dot with subnanometer precision. The method is based on measuring the orbital energies in a magnetic field with various strengths and orientations in the plane of the 2D electron gas. From such data, we deduce the microscopic confinement potential landscape and quantify the degree by which it differs from a harmonic oscillator potential. The spectroscopy is used to validate shape manipulation with gate voltages, agreeing with expectations from the gate layout. Our measurements demonstrate a versatile tool for quantum dots with one dominant axis of strong confinement.
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Affiliation(s)
- Leon C Camenzind
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Liuqi Yu
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Peter Stano
- Center for Emergent Matter Science, RIKEN, Saitama 351-0198, Japan
- Department of Applied Physics, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Institute of Physics, Slovak Academy of Sciences, 845 11 Bratislava, Slovakia
| | - Jeramy D Zimmerman
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Arthur C Gossard
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Center for Emergent Matter Science, RIKEN, Saitama 351-0198, Japan
| | - Dominik M Zumbühl
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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7
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Velasco J, Lee J, Wong D, Kahn S, Tsai HZ, Costello J, Umeda T, Taniguchi T, Watanabe K, Zettl A, Wang F, Crommie MF. Visualization and Control of Single-Electron Charging in Bilayer Graphene Quantum Dots. NANO LETTERS 2018; 18:5104-5110. [PMID: 30035544 DOI: 10.1021/acs.nanolett.8b01972] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Graphene p-n junctions provide an ideal platform for investigating novel behavior at the boundary between electronics and optics that arise from massless Dirac Fermions, such as whispering gallery modes and Veselago lensing. Bilayer graphene also hosts Dirac Fermions, but they differ from single-layer graphene charge carriers because they are massive, can be gapped by an applied perpendicular electric field, and have very different pseudospin selection rules across a p-n junction. Novel phenomena predicted for these massive Dirac Fermions at p-n junctions include anti-Klein tunneling, oscillatory Zener tunneling, and electron cloaked states. Despite these predictions there has been little experimental focus on the microscopic spatial behavior of massive Dirac Fermions in the presence of p-n junctions. Here we report the experimental manipulation and characterization of massive Dirac Fermions within bilayer graphene quantum dots defined by circular p-n junctions through the use of scanning tunneling microscopy-based (STM) methods. Our p-n junctions are created via a flexible technique that enables realization of exposed quantum dots in bilayer graphene/hBN heterostructures. These quantum dots exhibit sharp spectroscopic resonances that disperse in energy as a function of applied gate voltage. Spatial maps of these features show prominent concentric rings with diameters that can be tuned by an electrostatic gate. This behavior is explained by single-electron charging of localized states that arise from the quantum confinement of massive Dirac Fermions within our exposed bilayer graphene quantum dots.
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Affiliation(s)
- Jairo Velasco
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Department of Physics , University of California , Santa Cruz , California 95064 , United States
| | - Juwon Lee
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Dillon Wong
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Salman Kahn
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Hsin-Zon Tsai
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Joseph Costello
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Torben Umeda
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - 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
| | - Alex Zettl
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoSciences Institute at the University of California , Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Feng Wang
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoSciences Institute at the University of California , Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Michael F Crommie
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoSciences Institute at the University of California , Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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8
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On the origins of transport inefficiencies in mesoscopic networks. Sci Rep 2018; 8:3017. [PMID: 29445196 PMCID: PMC5812991 DOI: 10.1038/s41598-018-21250-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/01/2018] [Indexed: 11/13/2022] Open
Abstract
A counter-intuitive behavior analogous to the Braess paradox is encountered in a two-terminal mesoscopic network patterned in a two-dimensional electron system (2DES). Decreasing locally the electron density of one channel of the network paradoxically leads to an increased network electrical conductance. Our low temperature scanning gate microscopy experiments reveal different occurrences of such puzzling conductance variations, thanks to tip-induced localized modifications of electron flow throughout the network’s channels in the ballistic and coherent regime of transport. The robustness of the puzzling behavior is inspected by varying the global 2DES density, magnetic field and the tip-surface distance. Depending on the overall 2DES density, we show that either Coulomb Blockade resonances due to disorder-induced localized states or Fabry-Perot interferences tuned by the tip-induced electrostatic perturbation are at the origin of transport inefficiencies in the network, which are lifted when gradually closing one channel of the network with the tip.
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9
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Cabosart D, Felten A, Reckinger N, Iordanescu A, Toussaint S, Faniel S, Hackens B. Recurrent Quantum Scars in a Mesoscopic Graphene Ring. NANO LETTERS 2017; 17:1344-1349. [PMID: 28166405 DOI: 10.1021/acs.nanolett.6b03725] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
When coherent charge carriers cross micron-scale cavities, their dynamics can be governed by a few resonant states, also called "quantum scars", determined by the cavity geometry. Quantum scars can be described using theoretical tools but have also been directly imaged in the case of high-quality semiconductor cavities as well as in disordered graphene devices, thanks to scanning gate microscopy (SGM). Here, we discuss spatially resolved SGM images of low-temperature charge transport through a mesoscopic ring fabricated from high-quality monolayer graphene lying on top of hexagonal boron nitride. SGM images are decorated with a pattern of radial scars in the ring area, which is found to evolve smoothly and reappear when varying the charge-carrier energy. The energies separating recurrent patterns are found to be directly related to geometric dimensions of the ring. Moreover, a recurrence is also observed in simulations of the local density of states of a model graphene quantum ring. The observed recurrences are discussed in the light of recent predictions of relativistic quantum scars in mesoscopic graphene cavities.
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Affiliation(s)
- Damien Cabosart
- Nanoscopic Physics (NAPS), Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCL) , Chemin du Cyclotron 2 bte L7.01.07, B-1348 Louvain-la-Neuve, Belgium
| | - Alexandre Felten
- Research Centre in Physics of Matter and Radiation (PMR), University of Namur (UNamur) , 61 rue de Bruxelles, B-5000 Namur, Belgium
| | - Nicolas Reckinger
- Research Centre in Physics of Matter and Radiation (PMR), University of Namur (UNamur) , 61 rue de Bruxelles, B-5000 Namur, Belgium
| | - Andra Iordanescu
- Nanoscopic Physics (NAPS), Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCL) , Chemin du Cyclotron 2 bte L7.01.07, B-1348 Louvain-la-Neuve, Belgium
| | - Sébastien Toussaint
- Nanoscopic Physics (NAPS), Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCL) , Chemin du Cyclotron 2 bte L7.01.07, B-1348 Louvain-la-Neuve, Belgium
| | - Sébastien Faniel
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics/WINFAB, Université catholique de Louvain (UCL) , Place du Levant 3 bte L5.03.04, B-1348 Louvain-la-Neuve, Belgium
| | - Benoît Hackens
- Nanoscopic Physics (NAPS), Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCL) , Chemin du Cyclotron 2 bte L7.01.07, B-1348 Louvain-la-Neuve, Belgium
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10
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Miyahara Y, Roy-Gobeil A, Grutter P. Quantum state readout of individual quantum dots by electrostatic force detection. NANOTECHNOLOGY 2017; 28:064001. [PMID: 28059061 DOI: 10.1088/1361-6528/aa5261] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electric charge detection by atomic force microscopy (AFM) with single-electron resolution (e-EFM) is a promising way to investigate the electronic level structure of individual quantum dots (QDs). The oscillating AFM tip modulates the energy of the QDs, causing single electrons to tunnel between QDs and an electrode. The resulting oscillating electrostatic force changes the resonant frequency and damping of the AFM cantilever, enabling electrometry with a single-electron sensitivity. Quantitative electronic level spectroscopy is possible by sweeping the bias voltage. Charge stability diagram can be obtained by scanning the AFM tip around the QD. e-EFM technique enables to investigate individual colloidal nanoparticles and self-assembled QDs without nanoscale electrodes. e-EFM is a quantum electromechanical system where the back-action of a tunneling electron is detected by AFM; it can also be considered as a mechanical analog of admittance spectroscopy with a radio frequency resonator, which is emerging as a promising tool for quantum state readout for quantum computing. In combination with the topography imaging capability of the AFM, e-EFM is a powerful tool for investigating new nanoscale material systems which can be used as quantum bits.
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Affiliation(s)
- Yoichi Miyahara
- Department of Physics, McGill University, 3600 rue University, Montreal, H3A 2T8, Quebec, Canada
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11
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Matsunaga M, Higuchi A, He G, Yamada T, Krüger P, Ochiai Y, Gong Y, Vajtai R, Ajayan PM, Bird JP, Aoki N. Nanoscale-Barrier Formation Induced by Low-Dose Electron-Beam Exposure in Ultrathin MoS 2 Transistors. ACS NANO 2016; 10:9730-9737. [PMID: 27704777 DOI: 10.1021/acsnano.6b05952] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Utilizing an innovative combination of scanning-probe and spectroscopic techniques, supported by first-principles calculations, we demonstrate how electron-beam exposure of field-effect transistors, implemented from ultrathin molybdenum disulfide (MoS2), may cause nanoscale structural modifications that in turn significantly modify the electrical operation of these devices. Quite surprisingly, these modifications are induced by even the relatively low electron doses used in conventional electron-beam lithography, which are found to induce compressive strain in the atomically thin MoS2. Likely arising from sulfur-vacancy formation in the exposed regions, the strain gives rise to a local widening of the MoS2 bandgap, an idea that is supported both by our experiment and by the results of first-principles calculations. A nanoscale potential barrier develops at the boundary between exposed and unexposed regions and may cause extrinsic variations in the resulting electrical characteristics exhibited by the transistor. The widespread use of electron-beam lithography in nanofabrication implies that the presence of such strain must be carefully considered when seeking to harness the potential of atomically thin transistors. At the same time, this work also promises the possibility of exploiting the strain as a means to achieve "bandstructure engineering" in such devices.
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Affiliation(s)
| | | | - Guanchen He
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | | | | | | | - Yongji Gong
- Department of Materials Science and Nano-Engineering, Rice University , Houston, Texas 77005, United States
| | - Robert Vajtai
- Department of Materials Science and Nano-Engineering, Rice University , Houston, Texas 77005, United States
| | - Pulickel M Ajayan
- Department of Materials Science and Nano-Engineering, Rice University , Houston, Texas 77005, United States
| | - Jonathan P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York , Buffalo, New York 14260-1900, United States
| | - Nobuyuki Aoki
- Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
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12
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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 LETTERS 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] [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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13
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Zheng H, Weismann A, Berndt R. Tuning the electron transport at single donors in zinc oxide with a scanning tunnelling microscope. Nat Commun 2015; 5:2992. [PMID: 24390611 DOI: 10.1038/ncomms3992] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 11/22/2013] [Indexed: 11/09/2022] Open
Abstract
In devices like the single-electron transistor the detailed transport properties of a nanostructure can be measured by tuning its energy levels with a gate voltage. The scanning tunnelling microscope in contrast usually lacks such a gate electrode. Here we demonstrate tuning of the levels of a donor in a scanning tunnelling microscope without a third electrode. The potential and the position of the tip are used to locally control band bending. Conductance maps in this parameter space reveal Coulomb diamonds known from three-terminal data from single-electron transistors and provide information on charging transitions, binding energies and vibrational excitations. The analogy to single-electron transistor data suggests a new way of extracting these key quantities without making any assumptions about the unknown shape of the scanning tunnelling microscope tip.
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Affiliation(s)
- Hao Zheng
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
| | - Alexander Weismann
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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14
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Aoki N, da Cunha CR, Akis R, Ferry DK, Ochiai Y. Scanning gate imaging of a disordered quantum point contact. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:193202. [PMID: 24763258 DOI: 10.1088/0953-8984/26/19/193202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Scanning gate microscopy (SGM) is a novel technique that has been used to image characteristic features related to the coherent electron flow in mesoscopic structures. For instance, SGM has successfully been applied to study peculiar electron transport properties that arise due to small levels of disorder in a system. The particular case of an InGaAs quantum well layer in a heterostructure, which is dominated by a quasi-ballistic regime, was analyzed. A quantum point contact fabricated onto this material exhibits conduction fluctuations that are not expected in typical high-mobility heterostructures such as AlGaAs/GaAs. SGM revealed not only interference patterns corresponding to specific conductance fluctuations but also mode-dependent resistance peaks corresponding to the first and second quantum levels of conductance (2e(2)/h) at zero magnetic field. On the other hand, clear conductance plateaus originating from the integer quantum Hall effect were observed at high magnetic fields. The physical size of incompressible edge channels was estimated from cross-sectional analysis of these images.
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Affiliation(s)
- N Aoki
- Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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15
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Zhukov AA, Volk C, Winden A, Hardtdegen H, Schäpers T. The electronic transport of top subband and disordered sea in an InAs nanowire in the presence of a mobile gate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:165304. [PMID: 24694980 DOI: 10.1088/0953-8984/26/16/165304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We performed measurements at helium temperatures of the electronic transport in an InAs quantum wire (R(wire) ∼ 30 kΩ) in the presence of a charged tip of an atomic force microscope serving as a mobile gate. The period and the amplitude of the observed quasi-periodic oscillations are investigated in detail as a function of electron concentration in the linear and non-linear regime. We demonstrate the influence of the tip-to-sample distance on the ability to locally affect the top subband electrons as well as the electrons in the disordered sea. Furthermore, we introduce a new method of detection of the subband occupation in an InAs wire, which allows us to evaluate the number of electrons in the conductive band of the wire.
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Affiliation(s)
- A A Zhukov
- Institute of Solid State Physics, Russian Academy of Science, Chernogolovka, 142432, Russia
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16
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Coherent tunnelling across a quantum point contact in the quantum Hall regime. Sci Rep 2013; 3:1416. [PMID: 23475303 PMCID: PMC3593222 DOI: 10.1038/srep01416] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 02/22/2013] [Indexed: 12/03/2022] Open
Abstract
The unique properties of quantum hall devices arise from the ideal one-dimensional edge states that form in a two-dimensional electron system at high magnetic field. Tunnelling between edge states across a quantum point contact (QPC) has already revealed rich physics, like fractionally charged excitations, or chiral Luttinger liquid. Thanks to scanning gate microscopy, we show that a single QPC can turn into an interferometer for specific potential landscapes. Spectroscopy, magnetic field and temperature dependences of electron transport reveal a quantitatively consistent interferometric behavior of the studied QPC. To explain this unexpected behavior, we put forward a new model which relies on the presence of a quantum Hall island at the centre of the constriction as well as on different tunnelling paths surrounding the island, thereby creating a new type of interferometer. This work sets the ground for new device concepts based on coherent tunnelling.
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17
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Mantelli D, Cavaliere F, Sassetti M. Non-linear Coulomb blockade microscopy of a correlated one-dimensional quantum dot. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:432202. [PMID: 23041698 DOI: 10.1088/0953-8984/24/43/432202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We evaluate the chemical potential of a one-dimensional quantum dot coupled to an atomic force microscope tip. The dot is described within the Luttinger liquid framework, and the conductance peak positions as a function of the tip location are calculated in the linear and non-linear transport regimes for an arbitrary number of particles. The differences between the chemical potential oscillations induced by the Friedel and Wigner terms are carefully analysed in the whole range of interaction strengths. It is shown that Friedel oscillations, unlike the Wigner ones, are sensitive probes for detecting excited spin states and collective spin density waves involved in the transport.
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Affiliation(s)
- D Mantelli
- Dipartimento di Fisica, Università di Genova, Genova, Italy
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18
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Aoki N, Brunner R, Burke AM, Akis R, Meisels R, Ferry DK, Ochiai Y. Direct imaging of electron states in open quantum dots. PHYSICAL REVIEW LETTERS 2012; 108:136804. [PMID: 22540721 DOI: 10.1103/physrevlett.108.136804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Indexed: 05/31/2023]
Abstract
We use scanning gate microscopy to probe the ballistic motion of electrons within an open GaAs/AlGaAs quantum dot. Conductance maps are recorded by scanning a biased tip over the open quantum dot while a magnetic field is applied. We show that, for specific magnetic fields, the measured conductance images resemble the classical transmitted and backscattered trajectories and their quantum mechanical analogue. In addition, we prove experimentally, with this direct measurement technique, the existence of pointer states. The demonstrated direct imaging technique is essential for the fundamental understanding of wave function scarring and quantum decoherence theory.
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Affiliation(s)
- N Aoki
- Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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19
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Pala MG, Baltazar S, Liu P, Sellier H, Hackens B, Martins F, Bayot V, Wallart X, Desplanque L, Huant S. Transport inefficiency in branched-out mesoscopic networks: an analog of the Braess paradox. PHYSICAL REVIEW LETTERS 2012; 108:076802. [PMID: 22401236 DOI: 10.1103/physrevlett.108.076802] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Indexed: 05/31/2023]
Abstract
We present evidence for a counterintuitive behavior of semiconductor mesoscopic networks that is the analog of the Braess paradox encountered in classical networks. A numerical simulation of quantum transport in a two-branch mesoscopic network reveals that adding a third branch can paradoxically induce transport inefficiency that manifests itself in a sizable conductance drop of the network. A scanning-probe experiment using a biased tip to modulate the transmission of one branch in the network reveals the occurrence of this paradox by mapping the conductance variation as a function of the tip voltage and position.
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Affiliation(s)
- M G Pala
- IMEP-LAHC, Grenoble INP, Minatec, BP 257, Grenoble, France.
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20
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Huefner M, Schnez S, Kueng B, Ihn T, Reinwald M, Wegscheider W, Ensslin K. Mapping leakage currents in a nanostructure fabricated via local anodic oxidation. NANOTECHNOLOGY 2011; 22:295306. [PMID: 21693803 DOI: 10.1088/0957-4484/22/29/295306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The functionality of nanostructures fabricated via local anodic oxidation is limited by undesired leakage currents. We use low-temperature scanning gate microscopy to pin down the spatial position where leakage currents are most likely to occur. We show that leakage currents do not flow homogeneously along the complete barrier but at distinct weak points such as crossings of two oxide lines. These findings can be used to improve the design of such nanostructures.
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Affiliation(s)
- M Huefner
- Solid State Physics Laboratory, ETH Zürich, Zürich, Switzerland
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21
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Imaging Coulomb islands in a quantum Hall interferometer. Nat Commun 2010; 1:39. [PMID: 20975700 DOI: 10.1038/ncomms1038] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 06/24/2010] [Indexed: 11/08/2022] Open
Abstract
In the quantum Hall regime, near integer filling factors, electrons should only be transmitted through spatially separated edge states. However, in mesoscopic systems, electronic transmission turns out to be more complex, giving rise to a large spectrum of magnetoresistance oscillations. To explain these observations, recent models put forward the theory that, as edge states come close to each other, electrons can hop between counterpropagating edge channels, or tunnel through Coulomb islands. Here, we use scanning gate microscopy to demonstrate the presence of QH Coulomb islands, and reveal the spatial structure of transport inside a QH interferometer. Locations of electron islands are found by modulating the tunnelling between edge states and confined electron orbits. Tuning the magnetic field, we unveil a continuous evolution of active electron islands. This allows to decrypt the complexity of high-magnetic-field magnetoresistance oscillations, and opens the way to further local-scale manipulations of QH localized states.
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22
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Berezovsky J, Borunda MF, Heller EJ, Westervelt RM. Imaging coherent transport in graphene. Part I: mapping universal conductance fluctuations. NANOTECHNOLOGY 2010; 21:274013. [PMID: 20571200 DOI: 10.1088/0957-4484/21/27/274013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Graphene provides a fascinating testbed for new physics and exciting opportunities for future applications based on quantum phenomena. To understand the coherent flow of electrons through a graphene device, we employ a nanoscale probe that can access the relevant length scales--the tip of a liquid-He-cooled scanning probe microscope (SPM) capacitively couples to the graphene device below, creating a movable scatterer for electron waves. At sufficiently low temperatures and small size scales, the diffusive transport of electrons through graphene becomes coherent, leading to universal conductance fluctuations (UCF). By scanning the tip over a device, we map these conductance fluctuations versus scatterer position. We find that the conductance is highly sensitive to the tip position, producing delta G approximately e(2)/h fluctuations when the tip is displaced by a distance comparable to half the Fermi wavelength. These measurements are in good agreement with detailed quantum simulations of the imaging experiment and demonstrate the value of a cooled SPM for probing coherent transport in graphene.
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Affiliation(s)
- J Berezovsky
- School of Engineering and Applied Science, and Department of Physics, Harvard University, Cambridge, MA 02138, USA
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23
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Berezovsky J, Westervelt RM. Imaging coherent transport in graphene. Part II: probing weak localization. NANOTECHNOLOGY 2010; 21:274014. [PMID: 20571201 DOI: 10.1088/0957-4484/21/27/274014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Graphene has opened new avenues of research in quantum transport, with potential applications for coherent electronics. Coherent transport depends sensitively on scattering from microscopic disorder present in graphene samples: electron waves traveling along different paths interfere, changing the total conductance. Weak localization is produced by the coherent backscattering of waves, while universal conductance fluctuations are created by summing over all paths. In this work, we obtain conductance images of weak localization with a liquid-He-cooled scanning probe microscope, by using the tip to create a movable scatterer in a graphene device. This technique allows us to investigate coherent transport with a probe of size comparable to the electron wavelength. Images of magnetoconductance versus tip position map the effects of disorder by moving a single scatterer, revealing how electron interference is modified by the tip perturbation. The weak localization dip in conductivity at B = 0 is obtained by averaging magnetoconductance traces at different positions of the tip-created scatterer. The width Delta B(WL) of the dip yields an estimate of the electron coherence length L(phi) at fixed charge density. This 'scanning scatterer' method provides a new way of investigating coherent transport in graphene by directly perturbing the disorder configuration that creates these interferometric effects.
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Affiliation(s)
- Jesse Berezovsky
- School of Engineering and Applied Science, and Department of Physics, Harvard University, Cambridge, MA 02138, USA
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24
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Pala MG, Baltazar S, Martins F, Hackens B, Sellier H, Ouisse T, Bayot V, Huant S. Scanning gate microscopy of quantum rings: effects of an external magnetic field and of charged defects. NANOTECHNOLOGY 2009; 20:264021. [PMID: 19509453 DOI: 10.1088/0957-4484/20/26/264021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We study scanning gate microscopy (SGM) in open quantum rings obtained from buried semiconductor InGaAs/InAlAs heterostructures. By performing a theoretical analysis based on the Keldysh-Green function approach we interpret the radial fringes observed in experiments as the effect of randomly distributed charged defects. We associate SGM conductance images with the local density of states (LDOS) of the system. We show that such an association cannot be made with the current density distribution. By varying an external magnetic field we are able to reproduce recursive quasi-classical orbits in LDOS and conductance images, which bear the same periodicity as the Aharonov-Bohm effect.
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Affiliation(s)
- M G Pala
- IMEP-LAHC, Grenoble INP Minatec, BP 257, F-38016 Grenoble, France.
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25
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Freyn A, Kleftogiannis I, Pichard JL. Scanning gate microscopy of a nanostructure where electrons interact. PHYSICAL REVIEW LETTERS 2008; 100:226802. [PMID: 18643442 DOI: 10.1103/physrevlett.100.226802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Indexed: 05/26/2023]
Abstract
We show that scanning gate microscopy can be used for probing electron-electron interactions inside a nanostructure. We assume a simple model made of two noninteracting strips attached to an interacting nanosystem. In one of the strips, the electrostatic potential can be locally varied by a charged tip. This change induces corrections upon the nanosystem Hartree-Fock self-energies which enhance the fringes spaced by half the Fermi wavelength in the images giving the quantum conductance as a function of the tip position.
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Affiliation(s)
- Axel Freyn
- CEA, IRAMIS, Service de Physique de l'Etat Condensé (CNRS URA 2464), F-91191 Gif-sur-Yvette, France
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26
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Martins F, Hackens B, Pala MG, Ouisse T, Sellier H, Wallart X, Bollaert S, Cappy A, Chevrier J, Bayot V, Huant S. Imaging electron wave functions inside open quantum rings. PHYSICAL REVIEW LETTERS 2007; 99:136807. [PMID: 17930624 DOI: 10.1103/physrevlett.99.136807] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Indexed: 05/25/2023]
Abstract
Combining scanning gate microscopy (SGM) experiments and simulations, we demonstrate low temperature imaging of the electron probability density |Psi|(2)(x,y) in embedded mesoscopic quantum rings. The tip-induced conductance modulations share the same temperature dependence as the Aharonov-Bohm effect, indicating that they originate from electron wave function interferences. Simulations of both |Psi|(2)(x,y) and SGM conductance maps reproduce the main experimental observations and link fringes in SGM images to |Psi|(2)(x,y).
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Affiliation(s)
- F Martins
- Institut Néel, CNRS and Université Joseph Fourier, BP 166, 38042 Grenoble cedex 9, France
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27
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Bleszynski AC, Zwanenburg FA, Westervelt RM, Roest AL, Bakkers EPAM, Kouwenhoven LP. Scanned probe imaging of quantum dots inside InAs nanowires. NANO LETTERS 2007; 7:2559-62. [PMID: 17691848 DOI: 10.1021/nl0621037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We show how a scanning probe microscope (SPM) can be used to image electron flow through InAs nanowires, elucidating the physics of nanowire devices on a local scale. A charged SPM tip is used as a movable gate. Images of nanowire conductance versus tip position spatially map the conductance of InAs nanowires at liquid-He temperatures. Plots of conductance versus backgate voltage without the tip present show complex patterns of Coulomb-blockade peaks. Images of nanowire conductance identify their source as multiple quantum dots formed by disorder along the nanowire--each dot is surrounded by a series of concentric rings corresponding to Coulomb blockade peaks. An SPM image locates the dots and provides information about their size. In this way, SPM images can be used to understand the features that control transport through nanowires. The nanowires were grown from metal catalyst particles and have diameters approximately 80 nm and lengths 2-3 microm.
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Affiliation(s)
- Ania C Bleszynski
- Department of Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
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28
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Gildemeister AE, Ihn T, Barengo C, Studerus P, Ensslin K. Construction of a dilution refrigerator cooled scanning force microscope. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:013704. [PMID: 17503925 DOI: 10.1063/1.2431793] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We present a scanning force microscope that operates in a dilution refrigerator at temperatures of about 100 mK. We use tuning fork sensors for scanning gate experiments on mesoscopic semiconductor nanostructures. Slip-stick motors allow sample coarse-positioning at base temperature. The construction, thermal anchoring, and a procedure to optimize the settings of the phase-locked loop that we use for sensor control are discussed in detail. We present low-temperature topographic and scanning gate images as examples of successful operation.
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Affiliation(s)
- A E Gildemeister
- Laboratory of Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
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29
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Aoki N, Burke A, Cunha CRD, Akis R, Ferry DK, Ochiai Y. Study of quantum point contact via low temperature scanning gate microscopy. ACTA ACUST UNITED AC 2006. [DOI: 10.1088/1742-6596/38/1/020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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