1
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Haxell DZ, Cheah E, Křížek F, Schott R, Ritter MF, Hinderling M, Belzig W, Bruder C, Wegscheider W, Riel H, Nichele F. Measurements of Phase Dynamics in Planar Josephson Junctions and SQUIDs. Phys Rev Lett 2023; 130:087002. [PMID: 36898094 DOI: 10.1103/physrevlett.130.087002] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 09/15/2022] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
We experimentally investigate the stochastic phase dynamics of planar Josephson junctions (JJs) and superconducting quantum interference devices (SQUIDs) defined in epitaxial InAs/Al heterostructures, and characterized by a large ratio of Josephson energy to charging energy. We observe a crossover from a regime of macroscopic quantum tunneling to one of phase diffusion as a function of temperature, where the transition temperature T^{*} is gate-tunable. The switching probability distributions are shown to be consistent with a small shunt capacitance and moderate damping, resulting in a switching current which is a small fraction of the critical current. Phase locking between two JJs leads to a difference in switching current between that of a JJ measured in isolation and that of the same JJ measured in an asymmetric SQUID loop. In the case of the loop, T^{*} is also tuned by a magnetic flux.
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Affiliation(s)
- D Z Haxell
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - E Cheah
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - F Křížek
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - R Schott
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - M F Ritter
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - M Hinderling
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - W Belzig
- Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany
| | - C Bruder
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - H Riel
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - F Nichele
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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2
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Ritter MF, Crescini N, Haxell DZ, Hinderling M, Riel H, Bruder C, Fuhrer A, Nichele F. Out-of-equilibrium phonons in gated superconducting switches. Nat Electron 2022; 5:71-77. [PMID: 35310295 PMCID: PMC8885403 DOI: 10.1038/s41928-022-00721-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 01/19/2022] [Indexed: 06/13/2023]
Abstract
Recent experiments have suggested that superconductivity in metallic nanowires can be suppressed by the application of modest gate voltages. The source of this gate action has been debated and either attributed to an electric-field effect or to small leakage currents. Here we show that the suppression of superconductivity in titanium nitride nanowires on silicon substrates does not depend on the presence or absence of an electric field at the nanowire, but requires a current of high-energy electrons. The suppression is most efficient when electrons are injected into the nanowire, but similar results are obtained when electrons are passed between two remote electrodes. This is explained by the decay of high-energy electrons into phonons, which propagate through the substrate and affect superconductivity in the nanowire by generating quasiparticles. By studying the switching probability distribution of the nanowire, we also show that high-energy electron emission leads to a much broader phonon energy distribution compared with the case where superconductivity is suppressed by Joule heating near the nanowire.
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Affiliation(s)
- M. F. Ritter
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
| | - N. Crescini
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
| | - D. Z. Haxell
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
| | - M. Hinderling
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
| | - H. Riel
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
| | - C. Bruder
- Department of Physics, University of Basel, Basel, Switzerland
| | - A. Fuhrer
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
| | - F. Nichele
- IBM Quantum, IBM Research—Zurich, Rüschlikon, Switzerland
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3
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Whiticar AM, Fornieri A, O'Farrell ECT, Drachmann ACC, Wang T, Thomas C, Gronin S, Kallaher R, Gardner GC, Manfra MJ, Marcus CM, Nichele F. Coherent transport through a Majorana island in an Aharonov-Bohm interferometer. Nat Commun 2020; 11:3212. [PMID: 32587242 PMCID: PMC7316771 DOI: 10.1038/s41467-020-16988-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 05/17/2020] [Indexed: 11/29/2022] Open
Abstract
Majorana zero modes are leading candidates for topological quantum computation due to non-local qubit encoding and non-abelian exchange statistics. Spatially separated Majorana modes are expected to allow phase-coherent single-electron transport through a topological superconducting island via a mechanism referred to as teleportation. Here we experimentally investigate such a system by patterning an elongated epitaxial InAs-Al island embedded in an Aharonov-Bohm interferometer. With increasing parallel magnetic field, a discrete sub-gap state in the island is lowered to zero energy yielding persistent 1e-periodic Coulomb blockade conductance peaks (e is the elementary charge). In this condition, conductance through the interferometer is observed to oscillate in a perpendicular magnetic field with a flux period of h/e (h is Planck’s constant), indicating coherent transport of single electrons through the islands, a signature of electron teleportation via Majorana modes. Theories predict teleportation of phase-coherent single electrons through a topological superconducting island. Here, the authors report persistent Coulomb blockade conductance peaks due to coherent transport of single electrons through patterned InAs-Al islands embedded in an Aharonov-Bohm interferometer.
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Affiliation(s)
- A M Whiticar
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - A Fornieri
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - E C T O'Farrell
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - A C C Drachmann
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - T Wang
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - C Thomas
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - S Gronin
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - R Kallaher
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - G C Gardner
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - M J Manfra
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA.,School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.,School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - C M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark.
| | - F Nichele
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark. .,IBM Research - Zurich, Sumerstrasse 4, 8803, Rschlikon, Switzerland.
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4
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Nichele F, Portolés E, Fornieri A, Whiticar AM, Drachmann ACC, Gronin S, Wang T, Gardner GC, Thomas C, Hatke AT, Manfra MJ, Marcus CM. Relating Andreev Bound States and Supercurrents in Hybrid Josephson Junctions. Phys Rev Lett 2020; 124:226801. [PMID: 32567899 DOI: 10.1103/physrevlett.124.226801] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/03/2020] [Accepted: 04/27/2020] [Indexed: 06/11/2023]
Abstract
We demonstrate concomitant measurement of phase-dependent critical current and Andreev bound state spectrum in a highly transmissive InAs Josephson junction embedded in a dc superconducting quantum interference device (SQUID). Tunneling spectroscopy reveals Andreev bound states with near unity transmission probability. A nonsinusoidal current-phase relation is derived from the Andreev spectrum, showing excellent agreement with the one extracted from the SQUID critical current. Both measurements are reconciled within a short junction model where multiple Andreev bound states, with various transmission probabilities, contribute to the entire supercurrent flowing in the junction.
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Affiliation(s)
- F Nichele
- Center for Quantum Devices and Microsoft Quantum Lab-Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - E Portolés
- Center for Quantum Devices and Microsoft Quantum Lab-Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A Fornieri
- Center for Quantum Devices and Microsoft Quantum Lab-Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A M Whiticar
- Center for Quantum Devices and Microsoft Quantum Lab-Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A C C Drachmann
- Center for Quantum Devices and Microsoft Quantum Lab-Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - S Gronin
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- Microsoft Quantum Purdue, Purdue University, West Lafayette, Indiana 47907, USA
| | - T Wang
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - G C Gardner
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- Microsoft Quantum Purdue, Purdue University, West Lafayette, Indiana 47907, USA
| | - C Thomas
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - A T Hatke
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - M J Manfra
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
- Microsoft Quantum Purdue, Purdue University, West Lafayette, Indiana 47907, USA
| | - C M Marcus
- Center for Quantum Devices and Microsoft Quantum Lab-Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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5
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O'Farrell ECT, Drachmann ACC, Hell M, Fornieri A, Whiticar AM, Hansen EB, Gronin S, Gardner GC, Thomas C, Manfra MJ, Flensberg K, Marcus CM, Nichele F. Hybridization of Subgap States in One-Dimensional Superconductor-Semiconductor Coulomb Islands. Phys Rev Lett 2018; 121:256803. [PMID: 30608825 DOI: 10.1103/physrevlett.121.256803] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Indexed: 06/09/2023]
Abstract
We present measurements of one-dimensional superconductor-semiconductor Coulomb islands, fabricated by gate confinement of a two-dimensional InAs heterostructure with an epitaxial Al layer. When tuned via electrostatic side gates to regimes without subgap states, Coulomb blockade reveals Cooper-pair mediated transport. When subgap states are present, Coulomb peak positions and heights oscillate in a correlated way with magnetic field and gate voltage, as predicted theoretically, with (anti)crossings in (parallel) transverse magnetic field indicating Rashba-type spin-orbit coupling. Overall results are consistent with a picture of overlapping Majorana zero modes in finite wires.
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Affiliation(s)
- E C T O'Farrell
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A C C Drachmann
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - M Hell
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-22100 Lund, Sweden
| | - A Fornieri
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A M Whiticar
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - E B Hansen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - S Gronin
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - G C Gardner
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - C Thomas
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - M J Manfra
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - K Flensberg
- 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
| | - F Nichele
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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6
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Suominen HJ, Kjaergaard M, Hamilton AR, Shabani J, Palmstrøm CJ, Marcus CM, Nichele F. Zero-Energy Modes from Coalescing Andreev States in a Two-Dimensional Semiconductor-Superconductor Hybrid Platform. Phys Rev Lett 2017; 119:176805. [PMID: 29219474 DOI: 10.1103/physrevlett.119.176805] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Indexed: 06/07/2023]
Abstract
We investigate zero-bias conductance peaks that arise from coalescing subgap Andreev states, consistent with emerging Majorana zero modes, in hybrid semiconductor-superconductor wires defined in a two-dimensional InAs/Al heterostructure using top-down lithography and gating. The measurements indicate a hard superconducting gap, ballistic tunneling contact, and in-plane critical fields up to 3 T. Top-down lithography allows complex geometries, branched structures, and straightforward scaling to multicomponent devices compared to structures made from assembled nanowires.
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Affiliation(s)
- H J Suominen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - M Kjaergaard
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A R Hamilton
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - J Shabani
- California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA
- Center for Quantum Phenomena, Physics Department, New York University, New York 10031, USA
| | - C J Palmstrøm
- California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA
- Department of Electrical Engineering, University of California, Santa Barbara, California 93106, USA
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - C M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - F Nichele
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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7
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Drachmann ACC, Suominen HJ, Kjaergaard M, Shojaei B, Palmstrøm CJ, Marcus CM, Nichele F. Proximity Effect Transfer from NbTi into a Semiconductor Heterostructure via Epitaxial Aluminum. Nano Lett 2017; 17:1200-1203. [PMID: 28072541 DOI: 10.1021/acs.nanolett.6b04964] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate the transfer of the superconducting properties of NbTi, a large-gap high-critical-field superconductor, into an InAs heterostructure via a thin intermediate layer of epitaxial Al. Two device geometries, a Josephson junction and a gate-defined quantum point contact, are used to characterize interface transparency and the two-step proximity effect. In the Josephson junction, multiple Andreev reflections reveal near-unity transparency with an induced gap Δ* = 0.50 meV and a critical temperature of 7.8 K. Tunneling spectroscopy yields a hard induced gap in the InAs adjacent to the superconductor of Δ* = 0.43 meV with substructure characteristic of both Al and NbTi.
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Affiliation(s)
- A C C Drachmann
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute University of Copenhagen , Universitetsparken 5, 2100 Copenhagen, Denmark
| | - H J Suominen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute University of Copenhagen , Universitetsparken 5, 2100 Copenhagen, Denmark
| | - M Kjaergaard
- 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
| | - F Nichele
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute University of Copenhagen , Universitetsparken 5, 2100 Copenhagen, Denmark
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8
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Kjaergaard M, Nichele F, Suominen HJ, Nowak MP, Wimmer M, Akhmerov AR, Folk JA, Flensberg K, Shabani J, Palmstrøm CJ, Marcus CM. Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure. Nat Commun 2016; 7:12841. [PMID: 27682268 PMCID: PMC5056412 DOI: 10.1038/ncomms12841] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 08/08/2016] [Indexed: 12/11/2022] Open
Abstract
Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards topological matter is by coupling a 2D electron gas with strong spin–orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunnelling regime. When the QPC is in the open regime, we observe a first conductance plateau at 4e2/h, consistent with theory. The hard-gap semiconductor–superconductor system demonstrated here is amenable to top-down processing and provides a new avenue towards low-dissipation electronics and topological quantum systems. Interface transparency between 2D semiconductors and superconductors is a longstanding problem, seriously hindering potential applications. Here, using a new hybrid system, Kjaergaard et al. report quantized conductance doubling and a hard superconducting gap measured via a quantum point contact, indicating a near pristine interface.
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Affiliation(s)
- M Kjaergaard
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - F Nichele
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - H J Suominen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - M P Nowak
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 4056, 2600 GA Delft, The Netherlands.,QuTech, Delft University of Technology, PO Box 4056, 2600 GA Delft, The Netherlands.,AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Mickiewicza 30, 30-059 Kraków, Poland
| | - M Wimmer
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 4056, 2600 GA Delft, The Netherlands.,QuTech, Delft University of Technology, PO Box 4056, 2600 GA Delft, The Netherlands
| | - A R Akhmerov
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 4056, 2600 GA Delft, The Netherlands
| | - J A Folk
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T1Z1.,Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T1Z4
| | - K Flensberg
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - J Shabani
- California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA
| | - C J Palmstrøm
- California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA
| | - 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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