1
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Niu J, Bastiaans KM, Ge JF, Tomar R, Jesudasan J, Raychaudhuri P, Karrer M, Kleiner R, Koelle D, Barbier A, Driessen EFC, Blanter YM, Allan MP. Why Shot Noise Does Not Generally Detect Pairing in Mesoscopic Superconducting Tunnel Junctions. PHYSICAL REVIEW LETTERS 2024; 132:076001. [PMID: 38427861 DOI: 10.1103/physrevlett.132.076001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 10/13/2023] [Accepted: 12/01/2023] [Indexed: 03/03/2024]
Abstract
The shot noise in tunneling experiments reflects the Poissonian nature of the tunneling process. The shot-noise power is proportional to both the magnitude of the current and the effective charge of the carrier. Shot-noise spectroscopy thus enables us, in principle, to determine the effective charge q of the charge carriers of that tunnel. This can be used to detect electron pairing in superconductors: In the normal state, the noise corresponds to single electron tunneling (q=1e), while in the paired state, the noise corresponds to q=2e. Here, we use a newly developed amplifier to reveal that in typical mesoscopic superconducting junctions, the shot noise does not reflect the signatures of pairing and instead stays at a level corresponding to q=1e. We show that transparency can control the shot noise, and this q=1e is due to the large number of tunneling channels with each having very low transparency. Our results indicate that in typical mesoscopic superconducting junctions, one should expect q=1e noise and lead to design guidelines for junctions that allow the detection of electron pairing.
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Affiliation(s)
- Jiasen Niu
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| | - Koen M Bastiaans
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - Jian-Feng Ge
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
| | - Ruchi Tomar
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - John Jesudasan
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Pratap Raychaudhuri
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Max Karrer
- Physikalisches Institut, Center for Quantum Science (CQ) and LISA+, Universität Tübingen, D-72076 Tübingen, Germany
| | - Reinhold Kleiner
- Physikalisches Institut, Center for Quantum Science (CQ) and LISA+, Universität Tübingen, D-72076 Tübingen, Germany
| | - Dieter Koelle
- Physikalisches Institut, Center for Quantum Science (CQ) and LISA+, Universität Tübingen, D-72076 Tübingen, Germany
| | - Arnaud Barbier
- Institut de Radioastronomie Millimétrique (IRAM), Domaine Universitaire de Grenoble, 38400 Saint-Martin-d'Hères, France
| | - Eduard F C Driessen
- Institut de Radioastronomie Millimétrique (IRAM), Domaine Universitaire de Grenoble, 38400 Saint-Martin-d'Hères, France
| | - Yaroslav M Blanter
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, The Netherlands
- Fakultät für Physik, Ludwig-Maximilians-Universität, Schellingstrasse 4, München 80799, Germany
- Munich Center for Quantum Science and Technology (MCQST), München, Germany
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2
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Schneider L, Ton KT, Ioannidis I, Neuhaus-Steinmetz J, Posske T, Wiesendanger R, Wiebe J. Proximity superconductivity in atom-by-atom crafted quantum dots. Nature 2023; 621:60-65. [PMID: 37587348 PMCID: PMC10482682 DOI: 10.1038/s41586-023-06312-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 06/12/2023] [Indexed: 08/18/2023]
Abstract
Gapless materials in electronic contact with superconductors acquire proximity-induced superconductivity in a region near the interface1,2. Numerous proposals build on this addition of electron pairing to originally non-superconducting systems and predict intriguing phases of matter, including topological3-7, odd-frequency8, nodal-point9 or Fulde-Ferrell-Larkin-Ovchinnikov10 superconductivity. Here we investigate the most miniature example of the proximity effect on only a single spin-degenerate quantum level of a surface state confined in a quantum corral11 on a superconducting substrate, built atom by atom by a scanning tunnelling microscope. Whenever an eigenmode of the corral is pitched close to the Fermi energy by adjusting the size of the corral, a pair of particle-hole symmetric states enters the gap of the superconductor. We identify these as spin-degenerate Andreev bound states theoretically predicted 50 years ago by Machida and Shibata12, which had-so far-eluded detection by tunnel spectroscopy but were recently shown to be relevant for transmon qubit devices13,14. We further find that the observed anticrossings of the in-gap states are a measure of proximity-induced pairing in the eigenmodes of the quantum corral. Our results have direct consequences on the interpretation of impurity-induced in-gap states in superconductors, corroborate concepts to induce superconductivity into surface states and further pave the way towards superconducting artificial lattices.
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Affiliation(s)
- Lucas Schneider
- Department of Physics, Universität Hamburg, Hamburg, Germany.
| | - Khai That Ton
- Department of Physics, Universität Hamburg, Hamburg, Germany
| | - Ioannis Ioannidis
- I. Institute for Theoretical Physics, Universität Hamburg, Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging, Hamburg, Germany
| | | | - Thore Posske
- I. Institute for Theoretical Physics, Universität Hamburg, Hamburg, Germany
- The Hamburg Centre for Ultrafast Imaging, Hamburg, Germany
| | | | - Jens Wiebe
- Department of Physics, Universität Hamburg, Hamburg, Germany
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3
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Volkov PA, Wilson JH, Lucht KP, Pixley JH. Current- and Field-Induced Topology in Twisted Nodal Superconductors. PHYSICAL REVIEW LETTERS 2023; 130:186001. [PMID: 37204877 DOI: 10.1103/physrevlett.130.186001] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 12/06/2022] [Accepted: 03/13/2023] [Indexed: 05/21/2023]
Abstract
We show that interlayer current induces topological superconductivity in twisted bilayers of nodal superconductors. A bulk gap opens and achieves its maximum near a "magic" twist angle θ_{MA}. Chiral edge modes lead to a quantized thermal Hall effect at low temperatures. Furthermore, we show that an in-plane magnetic field creates a periodic lattice of topological domains with edge modes forming low-energy bands. We predict their signatures in scanning tunneling microscopy. Estimates for candidate materials indicate that twist angles θ∼θ_{MA} are optimal for observing the predicted effects.
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Affiliation(s)
- Pavel A Volkov
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Justin H Wilson
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
- Department of Physics and Astronomy, and Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Kevin P Lucht
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
| | - J H Pixley
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
- Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
- Physics Department, Princeton University, Princeton, New Jersey 08544, USA
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4
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Carrad DJ, Stampfer L, Ols Teins DG, Petersen CEN, Khan SA, Krogstrup P, Jespersen TS. Photon-Assisted Tunneling of High-Order Multiple Andreev Reflections in Epitaxial Nanowire Josephson Junctions. NANO LETTERS 2022; 22:6262-6267. [PMID: 35862144 DOI: 10.1021/acs.nanolett.2c01840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Semiconductor/superconductor hybrids exhibit a range of phenomena that can be exploited for the study of novel physics and the development of new technologies. Understanding the origin of the energy spectrum of such hybrids is therefore a crucial goal. Here, we study Josephson junctions defined by shadow epitaxy on InAsSb/Al nanowires. The devices exhibit gate-tunable supercurrents at low temperatures and multiple Andreev reflections (MARs) at finite voltage bias. Under microwave irradiation, photon-assisted tunneling (PAT) of MARs produces characteristic oscillating sidebands at quantized energies, which depend on MAR order, n, in agreement with a recently suggested modification of the classical Tien-Gordon equation. The scaling of the quantized energy spacings with microwave frequency provides independent confirmation of the effective charge, ne, transferred by the nth-order tunneling process. The measurements suggest PAT as a powerful method for assigning the origin of low-energy spectral features in hybrid Josephson devices.
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Affiliation(s)
- Damon James Carrad
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
| | - Lukas Stampfer
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Da Gs Ols Teins
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | | | - Sabbir A Khan
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Danish National Metrology Institute, Kogle Alle 5, 2970 Hørsholm, Denmark
| | - Peter Krogstrup
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Thomas Sand Jespersen
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
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5
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Thupakula U, Perrin V, Palacio-Morales A, Cario L, Aprili M, Simon P, Massee F. Coherent and Incoherent Tunneling into Yu-Shiba-Rusinov States Revealed by Atomic Scale Shot-Noise Spectroscopy. PHYSICAL REVIEW LETTERS 2022; 128:247001. [PMID: 35776485 DOI: 10.1103/physrevlett.128.247001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/27/2021] [Accepted: 05/18/2022] [Indexed: 06/15/2023]
Abstract
The pair breaking potential of individual magnetic impurities in s-wave superconductors generates localized states inside the superconducting gap commonly referred to as Yu-Shiba-Rusinov (YSR) states whose isolated nature makes them promising building blocks for artificial structures that may host Majorana fermions. One of the challenges in this endeavor is to understand their intrinsic lifetime, ℏ/Λ, which is expected to be limited by the inelastic coupling with the continuum thus leading to decoherence. Here we use shot-noise scanning tunneling microscopy to reveal that electron tunneling into superconducting 2H-NbSe_{2} mediated by YSR states is not Poissonian, but ordered as a function of time, as evidenced by a reduction of the noise. Moreover, our data show the concomitant transfer of charges e and 2e, indicating that incoherent single particle and coherent Andreev processes operate simultaneously. From the quantitative agreement between experiment and theory we obtain Λ=1 μeV≪k_{B}T demonstrating that shot noise can probe energy scales and timescales inaccessible by conventional spectroscopy whose resolution is thermally limited.
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Affiliation(s)
- U Thupakula
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
| | - V Perrin
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
| | - A Palacio-Morales
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
| | - L Cario
- Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, F-44000 Nantes, France
| | - M Aprili
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
| | - P Simon
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
| | - F Massee
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
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6
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Denisov A, Bubis A, Piatrusha S, Titova N, Nasibulin A, Becker J, Treu J, Ruhstorfer D, Koblmüller G, Tikhonov E, Khrapai V. Heat-Mode Excitation in a Proximity Superconductor. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:1461. [PMID: 35564170 PMCID: PMC9101060 DOI: 10.3390/nano12091461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/14/2022] [Accepted: 04/16/2022] [Indexed: 11/25/2022]
Abstract
Mesoscopic superconductivity deals with various quasiparticle excitation modes, only one of them-the charge-mode-being directly accessible for conductance measurements due to the imbalance in populations of quasi-electron and quasihole excitation branches. Other modes carrying heat or even spin, valley etc. currents populate the branches equally and are charge-neutral, which makes them much harder to control. This noticeable gap in the experimental studies of mesoscopic non-equilibrium superconductivity can be filled by going beyond the conventional DC transport measurements and exploiting spontaneous current fluctuations. Here, we perform such an experiment and investigate the transport of heat in an open hybrid device based on a superconductor proximitized InAs nanowire. Using shot noise measurements, we investigate sub-gap Andreev heat guiding along the superconducting interface and fully characterize it in terms of the thermal conductance on the order of Gth∼e2/h, tunable by a back gate voltage. Understanding of the heat-mode also uncovers its implicit signatures in the non-local charge transport. Our experiments open a direct pathway to probe generic charge-neutral excitations in superconducting hybrids.
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Affiliation(s)
- Artem Denisov
- Osipyan Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia; (A.D.); (A.B.); (S.P.); (E.T.)
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Anton Bubis
- Osipyan Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia; (A.D.); (A.B.); (S.P.); (E.T.)
- Skolkovo Institute of Science and Technology, Nobel Street 3, 121205 Moscow, Russia;
| | - Stanislau Piatrusha
- Osipyan Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia; (A.D.); (A.B.); (S.P.); (E.T.)
| | - Nadezhda Titova
- Institute of Physics, Technology, and Informational Systems, Moscow Pedagogical State University, 29 Malaya Pirogovskaya St, 119435 Moscow, Russia;
| | - Albert Nasibulin
- Skolkovo Institute of Science and Technology, Nobel Street 3, 121205 Moscow, Russia;
| | - Jonathan Becker
- Center for Nanotechnology and Nanomaterials, Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany; (J.B.); (J.T.); (D.R.); (G.K.)
| | - Julian Treu
- Center for Nanotechnology and Nanomaterials, Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany; (J.B.); (J.T.); (D.R.); (G.K.)
| | - Daniel Ruhstorfer
- Center for Nanotechnology and Nanomaterials, Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany; (J.B.); (J.T.); (D.R.); (G.K.)
| | - Gregor Koblmüller
- Center for Nanotechnology and Nanomaterials, Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany; (J.B.); (J.T.); (D.R.); (G.K.)
| | - Evgeny Tikhonov
- Osipyan Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia; (A.D.); (A.B.); (S.P.); (E.T.)
| | - Vadim Khrapai
- Osipyan Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia; (A.D.); (A.B.); (S.P.); (E.T.)
- Faculty of Physics, National Research University Higher School of Economics, 20 Myasnitskaya Street, 101000 Moscow, Russia
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7
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Tamir I, Caspari V, Rolf D, Lotze C, Franke KJ. Shot-noise measurements of single-atom junctions using a scanning tunneling microscope. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:023702. [PMID: 35232162 DOI: 10.1063/5.0078917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/26/2022] [Indexed: 06/14/2023]
Abstract
Current fluctuations related to the discreteness of charge passing through small constrictions are termed shot noise. This unavoidable noise provides both advantages-being a direct measurement of the transmitted particles' charge-and disadvantages-a main noise source in nanoscale devices operating at low temperature. While better understanding of shot noise is desired, the technical difficulties in measuring it result in relatively few experimental works, especially in single-atom structures. Here, we describe a local shot-noise measurement apparatus and demonstrate successful noise measurements through single-atom junctions. Our apparatus, based on a scanning tunneling microscope, operates at liquid helium temperatures. It includes a broadband commercial amplifier mounted in close proximity to the tunnel junction, thus reducing both the thermal noise and input capacitance that limit traditional noise measurements. The full capabilities of the microscope are maintained in the modified system, and a quick transition between different measurement modes is possible.
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Affiliation(s)
- Idan Tamir
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Verena Caspari
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Daniela Rolf
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Christian Lotze
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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8
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Bastiaans KM, Chatzopoulos D, Ge JF, Cho D, Tromp WO, van Ruitenbeek JM, Fischer MH, de Visser PJ, Thoen DJ, Driessen EFC, Klapwijk TM, Allan MP. Direct evidence for Cooper pairing without a spectral gap in a disordered superconductor above Tc. Science 2021; 374:608-611. [PMID: 34709897 DOI: 10.1126/science.abe3987] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Koen M Bastiaans
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, Netherlands
| | | | - Jian-Feng Ge
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, Netherlands
| | - Doohee Cho
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Willem O Tromp
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, Netherlands
| | | | - Mark H Fischer
- Department of Physics, University of Zurich, 8057 Zurich, Switzerland
| | - Pieter J de Visser
- SRON Netherlands Institute for Space Research, 2333 CA Leiden Netherlands
| | - David J Thoen
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, Netherlands.,Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, 2628 CD Delft, Netherlands
| | - Eduard F C Driessen
- Institut de Radioastronomie Millimétrique (IRAM), Grenoble, 38400 Saint-Martin-d'Hères, France
| | - Teunis M Klapwijk
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, Netherlands.,Institute of Topological Materials, Julius-Maximilian-Universität Würzburg, 97070 Würzburg, Germany
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, 2333 CA Leiden, Netherlands
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9
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Electron pairing in the pseudogap state revealed by shot noise in copper oxide junctions. Nature 2019; 572:493-496. [PMID: 31435059 DOI: 10.1038/s41586-019-1486-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 06/18/2019] [Indexed: 11/08/2022]
Abstract
In the quest to understand high-temperature superconductivity in copper oxides, debate has been focused on the pseudogap-a partial energy gap that opens over portions of the Fermi surface in the 'normal' state above the bulk critical temperature1. The pseudogap has been attributed to precursor superconductivity, to the existence of preformed pairs and to competing orders such as charge-density waves1-4. A direct determination of the charge of carriers as a function of temperature and bias could help resolve among these alternatives. Here we report measurements of the shot noise of tunnelling current in high-quality La2-xSrxCuO4/La2CuO4/La2-xSrxCuO4 (LSCO/LCO/LSCO) heterostructures fabricated using atomic layer-by-layer molecular beam epitaxy at several doping levels. The data delineate three distinct regions in the bias voltage-temperature space. Well outside the superconducting gap region, the shot noise agrees quantitatively with independent tunnelling of individual charge carriers. Deep within the superconducting gap, shot noise is greatly enhanced, reminiscent of multiple Andreev reflections5-7. Above the critical temperature and extending to biases much larger than the superconducting gap, there is a broad region in which the noise substantially exceeds theoretical expectations for single-charge tunnelling, indicating pairing of charge carriers. These pairs are detectable deep into the pseudogap region of temperature and bias. The presence of these pairs constrains current models of the pseudogap and broken symmetry states, while phase fluctuations limit the domain of superconductivity.
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10
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Bastiaans KM, Benschop T, Chatzopoulos D, Cho D, Dong Q, Jin Y, Allan MP. Amplifier for scanning tunneling microscopy at MHz frequencies. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:093709. [PMID: 30278769 DOI: 10.1063/1.5043267] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/09/2018] [Indexed: 06/08/2023]
Abstract
Conventional scanning tunneling microscopy (STM) is limited to a bandwidth of a few kHz around DC. Here, we develop, build, and test a novel amplifier circuit capable of measuring the tunneling current in the MHz regime while simultaneously performing conventional STM measurements. This is achieved with an amplifier circuit including a LC tank with a quality factor exceeding 600 and a home-built, low-noise high electron mobility transistor. The amplifier circuit functions while simultaneously scanning with atomic resolution in the tunneling regime, i.e., at junction resistances in the range of giga-ohms, and down towards point contact spectroscopy. To enable high signal-to-noise ratios and meet all technical requirements for the inclusion in a commercial low temperature, ultra-high vacuum STM, we use superconducting cross-wound inductors and choose materials and circuit elements with low heat load. We demonstrate the high performance of the amplifier by spatially mapping the Poissonian noise of tunneling electrons on an atomically clean Au(111) surface. We also show differential conductance spectroscopy measurements at 3 MHz, demonstrating superior performance over conventional spectroscopy techniques. Further, our technology could be used to perform impedance matched spin resonance and distinguish Majorana modes from more conventional edge states.
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Affiliation(s)
- K M Bastiaans
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - T Benschop
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - D Chatzopoulos
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - D Cho
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - Q Dong
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - Y Jin
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - M P Allan
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
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11
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Massee F, Dong Q, Cavanna A, Jin Y, Aprili M. Atomic scale shot-noise using cryogenic MHz circuitry. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:093708. [PMID: 30278734 DOI: 10.1063/1.5043261] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/12/2018] [Indexed: 06/08/2023]
Abstract
By implementing dedicated cryogenic circuitry operating in the MHz regime, we have developed a scanning tunneling microscope (STM) capable of conventional, low frequency (<10 kHz), microscopy as well spectroscopy and shot-noise detection at 1 MHz. After calibrating our AC circuit on a gold surface, we illustrate our capability to detect shot-noise at the atomic scale and at low currents (<1 nA) by simultaneously measuring the atomically resolved differential conductance and shot-noise on the high temperature superconductor Bi2Sr2CaCu2O8+x . We further show our direct sensitivity to the temperature of the tunneling electrons at low voltages. Our MHz circuitry opens up the possibility to study charge and correlation effects at the atomic scale in all materials accessible to STM.
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Affiliation(s)
- F Massee
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
| | - Q Dong
- Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Sud, Université Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - A Cavanna
- Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Sud, Université Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - Y Jin
- Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Sud, Université Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - M Aprili
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405 Orsay, France
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12
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Quay CHL, Aprili M. Out-of-equilibrium spin transport in mesoscopic superconductors. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2015.0342. [PMID: 29941629 PMCID: PMC6030150 DOI: 10.1098/rsta.2015.0342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/16/2016] [Indexed: 06/08/2023]
Abstract
The excitations in conventional superconductors, Bogoliubov quasi-particles, are spin-[Formula: see text] fermions but their charge is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) spin and charge degrees of freedom may be separated. In this article, we review spin injection into conventional superconductors and focus on recent experiments on mesoscopic superconductors. We show how quasi-particle spin transport and out-of-equilibrium spin-dependent superconductivity can be triggered using the Zeeman splitting of the quasi-particle density of states in thin-film superconductors with small spin-mixing scattering. Finally, we address the spin dynamics and the feedback of quasi-particle spin imbalances on the amplitude of the superconducting energy gap.This article is part of the theme issue 'Andreev bound states'.
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Affiliation(s)
- C H L Quay
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université, Paris-Saclay, 91405 Orsay, France
| | - M Aprili
- Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université, Paris-Saclay, 91405 Orsay, France
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Nonlocal supercurrent of quartets in a three-terminal Josephson junction. Proc Natl Acad Sci U S A 2018; 115:6991-6994. [PMID: 29915041 DOI: 10.1073/pnas.1800044115] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A novel nonlocal supercurrent, carried by quartets, each consisting of four electrons, is expected to appear in a voltage-biased three-terminal Josephson junction. This supercurrent results from a nonlocal Andreev bound state (ABS), formed among three superconducting terminals. While in a two-terminal Josephson junction the usual ABS, and thus the dc Josephson current, exists only in equilibrium, the ABS, which gives rise to the quartet supercurrent, persists in the nonlinear regime. In this work, we report such resonance in a highly coherent three-terminal Josephson junction made in an InAs nanowire in proximity to an aluminum superconductor. In addition to nonlocal conductance measurements, cross-correlation measurements of current fluctuations provided a distinctive signature of the quartet supercurrent. Multiple device geometries had been tested, allowing us to rule out competing mechanisms and to establish the underlying microscopic origin of this coherent nondissipative current.
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Moca CP, Mora C, Weymann I, Zaránd G. Noise of a Chargeless Fermi Liquid. PHYSICAL REVIEW LETTERS 2018; 120:016803. [PMID: 29350969 DOI: 10.1103/physrevlett.120.016803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 10/17/2017] [Indexed: 06/07/2023]
Abstract
We construct a Fermi liquid theory to describe transport in a superconductor-quantum dot-normal metal junction close to the singlet-doublet (parity changing) transition of the dot. Though quasiparticles do not have a definite charge in this chargeless Fermi liquid, in the case of particle-hole symmetry, a mapping to the Anderson model unveils a hidden U(1) symmetry and a corresponding pseudocharge. In contrast to other correlated Fermi liquids, the back scattering noise reveals an effective charge equal to the charge of Cooper pairs, e^{*}=2e. In addition, we find a strong suppression of noise when the linear conductance is unitary, even for its nonlinear part.
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Affiliation(s)
- Cătălin Paşcu Moca
- BME-MTA Exotic Quantum Phase Group, Institute of Physics, Budapest University of Technology and Economics, H-1521 Budapest, Hungary
- Department of Physics, University of Oradea, 410087 Oradea, Romania
| | - Christophe Mora
- Laboratoire Pierre Aigrain, École Normale Supérieure, Université Paris 7 Diderot, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - Ireneusz Weymann
- Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - Gergely Zaránd
- BME-MTA Exotic Quantum Phase Group, Institute of Physics, Budapest University of Technology and Economics, H-1521 Budapest, Hungary
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Abstract
The control and measurement of local non-equilibrium configurations is of utmost importance in applications on energy harvesting, thermoelectrics and heat management in nano-electronics. This challenging task can be achieved with the help of various local probes, prominent examples including superconducting or quantum dot based tunnel junctions, classical and quantum resistors, and Raman thermography. Beyond time-averaged properties, valuable information can also be gained from spontaneous fluctuations of current (noise). From these perspective, however, a fundamental constraint is set by current conservation, which makes noise a characteristic of the whole conductor, rather than some part of it. Here we demonstrate how to remove this obstacle and pick up a local noise temperature of a current biased diffusive conductor with the help of a miniature noise probe. This approach is virtually noninvasive for the electronic energy distributions and extends primary local measurements towards strongly non-equilibrium regimes.
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