1
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Yadav S, Aloysius RP, Gupta G, Sahoo S. Granularity mediated multiple reentrances with negative magnetoresistance in disordered TiN thin films. Sci Rep 2023; 13:22701. [PMID: 38123674 PMCID: PMC10733403 DOI: 10.1038/s41598-023-50091-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 12/15/2023] [Indexed: 12/23/2023] Open
Abstract
Granular superconductors are the common examples of experimentally accessible model systems which can be used to explore various fascinating quantum phenomena that are fundamentally important and technologically relevant. One such phenomenon is the occurrence of reentrant resistive states in granular superconductors. Here, we report the observation of multiple reentrant resistive states for a disordered TiN thin film in its temperature and magnetic field dependent resistance measurements, R(T) and R(B), respectively. At each of the peak-temperatures corresponding to the zero-field R(T), a resistance peak appears in the R(B) around zero field which leads to a negative magnetoresistance (MR) region in its surrounding. These low-field negative MR regions appear for both perpendicular and parallel field directions with relatively higher amplitude and larger width for the parallel field. By adopting a granularity-based model, we show that the superconducting fluctuations in granular superconductors may lead to the observed reentrant states and the corresponding negative MR. Here, we propose that the reduction in the density of states in the fermionic channel due to the formation of Cooper pairs leads to the reentrant resistive state and the competition between the conduction processes in the single particle and Cooper channels result into the multiple resistive reentrances.
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Affiliation(s)
- Sachin Yadav
- CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - R P Aloysius
- CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Govind Gupta
- CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Sangeeta Sahoo
- CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
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2
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Adhikari R, Faina B, Ney V, Vorhauer J, Sterrer A, Ney A, Bonanni A. Effect of Impurity Scattering on Percolation of Bosonic Islands and Superconductivity in Fe Implanted NbN Thin Films. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3105. [PMID: 36144891 PMCID: PMC9505447 DOI: 10.3390/nano12183105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/25/2022] [Accepted: 09/03/2022] [Indexed: 06/16/2023]
Abstract
A reentrant temperature dependence of the thermoresistivity ρxx(T) between an onset local superconducting ordering temperature Tloconset and a global superconducting transition at T=Tglooffset has been reported in disordered conventional 3-dimensional (3D) superconductors. The disorder of these superconductors is a result of either an extrinsic granularity due to grain boundaries, or of an intrinsic granularity ascribable to the electronic disorder originating from impurity dopants. Here, the effects of Fe doping on the electronic properties of sputtered NbN layers with a nominal thickness of 100 nm are studied by means of low-T/high-μ0H magnetotransport measurements. The doping of NbN is achieved via implantation of 35 keV Fe ions. In the as-grown NbN films, a local onset of superconductivity at Tloconset=15.72K is found, while the global superconducting ordering is achieved at Tglooffset=15.05K, with a normal state resistivity ρxx=22μΩ·cm. Moreover, upon Fe doping of NbN, ρxx=40μΩ·cm is estimated, while Tloconset and Tglooffset are measured to be 15.1 K and 13.5 K, respectively. In Fe:NbN, the intrinsic granularity leads to the emergence of a bosonic insulator state and the normal-metal-to-superconductor transition is accompanied by six different electronic phases characterized by a N-shaped T dependence of ρxx(T). The bosonic insulator state in a s-wave conventional superconductor doped with dilute magnetic impurities is predicted to represent a workbench for emergent phenomena, such as gapless superconductivity, triplet Cooper pairings and topological odd frequency superconductivity.
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Affiliation(s)
- Rajdeep Adhikari
- Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria
| | | | | | | | | | | | - Alberta Bonanni
- Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria
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3
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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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4
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A robust nitridation technique for fabrication of disordered superconducting TiN thin films featuring phase slip events. Sci Rep 2021; 11:7888. [PMID: 33846407 PMCID: PMC8042045 DOI: 10.1038/s41598-021-86819-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/19/2021] [Indexed: 12/05/2022] Open
Abstract
Disorder induced phase slip (PS) events appearing in the current voltage characteristics (IVCs) are reported for two-dimensional TiN thin films produced by a robust substrate mediated nitridation technique. Here, high temperature annealing of Ti/Si3N4 based metal/substrate assembly is the key to produce majority phase TiN accompanied by TiSi2 & elemental Si as minority phases. The method itself introduces different level of disorder intrinsically by tuning the amount of the non-superconducting minority phases that are controlled by annealing temperature (Ta) and the film thickness. The superconducting critical temperature (Tc) strongly depends on Ta and the maximum Tc obtained from the demonstrated technique is about 4.8 K for the thickness range ~ 12 nm and above. Besides, the dynamics of IVCs get modulated by the appearance of intermediated resistive steps for decreased Ta and the steps get more prominent for reduced thickness. Further, the deviation in the temperature dependent critical current (Ic) from the Ginzburg–Landau theoretical limit varies strongly with the thickness. Finally, the Tc, intermediate resistive steps in the IVCs and the depairing current are observed to alter in a similar fashion with Ta and the thickness indicating the robustness of the synthesis process to fabricate disordered nitride-based superconductor.
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5
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Troyan IA, Semenok DV, Kvashnin AG, Sadakov AV, Sobolevskiy OA, Pudalov VM, Ivanova AG, Prakapenka VB, Greenberg E, Gavriliuk AG, Lyubutin IS, Struzhkin VV, Bergara A, Errea I, Bianco R, Calandra M, Mauri F, Monacelli L, Akashi R, Oganov AR. Anomalous High-Temperature Superconductivity in YH 6. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006832. [PMID: 33751670 DOI: 10.1002/adma.202006832] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 12/25/2020] [Indexed: 06/12/2023]
Abstract
Pressure-stabilized hydrides are a new rapidly growing class of high-temperature superconductors, which is believed to be described within the conventional phonon-mediated mechanism of coupling. Here, the synthesis of one of the best-known high-TC superconductors-yttrium hexahydride I m 3 ¯ m -YH6 is reported, which displays a superconducting transition at ≈224 K at 166 GPa. The extrapolated upper critical magnetic field Bc2 (0) of YH6 is surprisingly high: 116-158 T, which is 2-2.5 times larger than the calculated value. A pronounced shift of TC in yttrium deuteride YD6 with the isotope coefficient 0.4 supports the phonon-assisted superconductivity. Current-voltage measurements show that the critical current IC and its density JC may exceed 1.75 A and 3500 A mm-2 at 4 K, respectively, which is higher than that of the commercial superconductors, such as NbTi and YBCO. The results of superconducting density functional theory (SCDFT) and anharmonic calculations, together with anomalously high critical magnetic field, suggest notable departures of the superconducting properties from the conventional Migdal-Eliashberg and Bardeen-Cooper-Schrieffer theories, and presence of an additional mechanism of superconductivity.
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Affiliation(s)
- Ivan A Troyan
- Shubnikov Institute of Crystallography, Federal Scientific Research Center Crystallography and Photonics, Russian Academy of Sciences, 59 Leninskii Prospect, Moscow, 119333, Russia
| | - Dmitrii V Semenok
- Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, 3 Nobel Street, Moscow, 121025, Russia
| | - Alexander G Kvashnin
- Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, 3 Nobel Street, Moscow, 121025, Russia
| | - Andrey V Sadakov
- P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Oleg A Sobolevskiy
- P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Vladimir M Pudalov
- P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991, Russia
- National Research University, Higher School of Economics, Moscow, 101000, Russia
| | - Anna G Ivanova
- Shubnikov Institute of Crystallography, Federal Scientific Research Center Crystallography and Photonics, Russian Academy of Sciences, 59 Leninskii Prospect, Moscow, 119333, Russia
| | - Vitali B Prakapenka
- Center for Advanced Radiation Sources, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL, 60637, USA
| | - Eran Greenberg
- Center for Advanced Radiation Sources, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL, 60637, USA
| | - Alexander G Gavriliuk
- Shubnikov Institute of Crystallography, Federal Scientific Research Center Crystallography and Photonics, Russian Academy of Sciences, 59 Leninskii Prospect, Moscow, 119333, Russia
- Institute for Nuclear Research, Russian Academy of Sciences, Fizicheskaya str. 27, Troitsk, Moscow, 108840, Russia
| | - Igor S Lyubutin
- Shubnikov Institute of Crystallography, Federal Scientific Research Center Crystallography and Photonics, Russian Academy of Sciences, 59 Leninskii Prospect, Moscow, 119333, Russia
| | - Viktor V Struzhkin
- Center for High Pressure Science and Technology Advanced Research, Shanghai, 201203, China
| | - Aitor Bergara
- Centro de Física de Materiales CFM, CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, Basque Country, Donostia, 20018, Spain
- Departamento de Física de la Materia Condensada, University of the Basque Country (UPV/EHU), Basque Country, Bilbao, 48080, Spain
- Donostia International Physics Center (DIPC), Manuel Lardizabal pasealekua 4, Basque Country, Donostia, 20018, Spain
| | - Ion Errea
- Centro de Física de Materiales CFM, CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, Basque Country, Donostia, 20018, Spain
- Donostia International Physics Center (DIPC), Manuel Lardizabal pasealekua 4, Basque Country, Donostia, 20018, Spain
- Fisika Aplikatua 1 Saila, University of the Basque Country (UPV/EHU), Europa plaza 1, Donostia, 20018, Spain
| | - Raffaello Bianco
- Centro de Física de Materiales CFM, CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, Basque Country, Donostia, 20018, Spain
| | - Matteo Calandra
- Departimento di Fisica, Università di Trento, Via Sommarive 14, Povo, 38123, Italy
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, Paris, F-75252, France
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, Genova, I-16163, Italy
| | - Francesco Mauri
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, Paris, F-75252, France
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, Genova, I-16163, Italy
| | - Lorenzo Monacelli
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, Genova, I-16163, Italy
- Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, Roma, I-00185, Italy
| | - Ryosuke Akashi
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-8654, Japan
| | - Artem R Oganov
- Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, 3 Nobel Street, Moscow, 121025, Russia
- Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, Roma, I-00185, Italy
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-8654, Japan
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6
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Superconducting phase transitions in disordered NbTiN films. Sci Rep 2020; 10:1471. [PMID: 32001735 PMCID: PMC6992621 DOI: 10.1038/s41598-020-58192-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 01/13/2020] [Indexed: 11/08/2022] Open
Abstract
Suppression of superconductivity in disordered systems is a fundamental problem of condensed matter physics. Here we investigate superconducting niobium-titanium-nitride (Nb1-xTixN) thin films grown by the atomic layer deposition (ALD) with slightly different growth process parameters. We observe a smooth crossover from the disorder-driven superconductor-normal metal transition (SMT) to the superconductor-insulator transition (SIT) via the intermediate Bose metal state detected by the low-temperature saturation of the temperature dependence of the sheet resistance. We demonstrate that the SIT via the intervening Bose metal state occurs if the sheet resistance of the film in the maximum, Rmax prior to the superconducting drop of R(T), exceeds Rq = h/4e2.
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7
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Zhao SYF, Poccia N, Panetta MG, Yu C, Johnson JW, Yoo H, Zhong R, Gu GD, Watanabe K, Taniguchi T, Postolova SV, Vinokur VM, Kim P. Sign-Reversing Hall Effect in Atomically Thin High-Temperature Bi_{2.1}Sr_{1.9}CaCu_{2.0}O_{8+δ} Superconductors. PHYSICAL REVIEW LETTERS 2019; 122:247001. [PMID: 31322397 DOI: 10.1103/physrevlett.122.247001] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 01/31/2019] [Indexed: 06/10/2023]
Abstract
We developed novel techniques to fabricate atomically thin Bi_{2.1}Sr_{1.9}CaCu_{2.0}O_{8+δ} van der Waals heterostructures down to two unit cells while maintaining a transition temperature T_{c} close to the bulk, and carry out magnetotransport measurements on these van der Waals devices. We find a double sign change of the Hall resistance R_{xy} as in the bulk system, spanning both below and above T_{c}. Further, we observe a drastic enlargement of the region of sign reversal in the temperature-magnetic field phase diagram with decreasing thickness of the device. We obtain quantitative agreement between experimental R_{xy}(T,B) and the predictions of the vortex dynamics-based description of Hall effect in high-temperature superconductors both above and below T_{c}.
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Affiliation(s)
- S Y Frank Zhao
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Nicola Poccia
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Margaret G Panetta
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Cyndia Yu
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Jedediah W Johnson
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Hyobin Yoo
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Ruidan Zhong
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - G D Gu
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Svetlana V Postolova
- Institute for Physics of Microstructures RAS, Nizhny Novgorod 603950, Russia
- Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090, Russia
| | - Valerii M Vinokur
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Consortium for Advanced Science and Engineering, Office of Research and National Laboratories, University of Chicago, Chicago, Illinois 60637, USA
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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8
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Mironov AY, Postolova SV, Baturina TI. Quantum contributions to the magnetoconductivity of critically disordered superconducting TiN films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:485601. [PMID: 30418946 DOI: 10.1088/1361-648x/aae870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The onset of superconductivity in the presence of disorder is a fundamental problem of condensed matter physics. Here we investigate the magnetoconductance of disordered ([Formula: see text]) superconducting TiN films above the critical temperature T c. We show that the magnetoconductivity of moderately disordered films with [Formula: see text] is in full agreement with the perturbative theory of quantum contributions to conductivity. We demonstrate that the magnetoconductivity of films with [Formula: see text] is also in agreement with the perturbative theory down to temperatures [Formula: see text]. The quantitative discrepancy between experiment and theory develops only below temperatures [Formula: see text] for films with [Formula: see text]. This discrepancy can be eliminated if we assume steeper temperature dependence of the Larkin's electron-electron attraction strength, [Formula: see text]. The obtained temperature dependence of electron phase breaking time [Formula: see text] is in agreement with theoretical predictions for all samples.
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Affiliation(s)
- A Yu Mironov
- Department of Physics, Novosibirsk State University, 2 Pirogova Str., 630090 Novosibirsk, Russia. A V Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentjev Av., 630090 Novosibirsk, Russia
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9
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Qiao L, Li D, Postolova SV, Mironov AY, Vinokur V, Rosenstein B. Dynamical instability of the electric transport in superconductors. Sci Rep 2018; 8:14104. [PMID: 30237416 PMCID: PMC6147792 DOI: 10.1038/s41598-018-32302-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 09/05/2018] [Indexed: 11/09/2022] Open
Abstract
We develop a nonlinear theory of the electronic transport in superconductors in the framework of the time-dependent Ginzburg-Landau (TDGL) equation. We utilize self-consistent Gaussian approximation and reveal the conditions under which the current-voltage V(I) dependence (I-V characteristics) acquires an S-shape form leading to switching instabilities. We demonstrate that in two-dimensions the emergence of such an instability is a hallmark of the Berezinskii-Kosterlitz-Thouless (BKT) transition that we have detected by transport measurements of titanium nitride (TiN) films. Our theoretical findings compare favorably with our experimental results.
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Affiliation(s)
- Lei Qiao
- School of Physics, Peking University, Beijing, 100871, China.,Collaborative Innovation Center of Quantum Matter, Beijing, China
| | - Dingping Li
- School of Physics, Peking University, Beijing, 100871, China.,Collaborative Innovation Center of Quantum Matter, Beijing, China
| | - Svetlana V Postolova
- Institute for Physics of Microstructures RAS, GSP-105, Nizhny Novgorod, 603950, Russia.,A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, 630090, Russia
| | - Alexey Yu Mironov
- A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, 630090, Russia. .,Department of Physics, Novosibirsk State University, Novosibirsk, 630090, Russia.
| | - Valerii Vinokur
- Argonne National Laboratory, Materials Science Division, Lemont, IL, 60439, USA
| | - Baruch Rosenstein
- Electrophysics Department, National Chiao Tung University, Hsinchu, 30050, Taiwan, Republic of China. .,Physics Department, Bar-Ilan University, 52900, Ramat-Gan, Israel.
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10
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Roy A, Shimshoni E, Frydman A. Quantum Criticality at the Superconductor-Insulator Transition Probed by the Nernst Effect. PHYSICAL REVIEW LETTERS 2018; 121:047003. [PMID: 30095933 DOI: 10.1103/physrevlett.121.047003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Indexed: 06/08/2023]
Abstract
The superconductor-insulator transition (SIT) is an excellent example of a quantum phase transition at zero temperature, dominated by quantum fluctuations. These are expected to be very prominent close to the quantum critical point. So far, most of the experimental studies of the SIT have concentrated on transport properties and tunneling experiments that provide indirect information on criticality close to the transition. Here we present an experiment uniquely designed to study the evolution of quantum fluctuations through the quantum critical point. We utilize the Nernst effect, which has been shown to be effective in probing superconducting fluctuation. We measure the Nernst coefficient in amorphous indium oxide films tuned through the SIT and find a large signal on both the superconducting and the insulating sides, which peaks close to the critical point. The transverse Peltier coefficient α_{xy}, which is the thermodynamic quantity extracted from these measurements, follows quantum critical scaling with critical exponents ν∼0.7 and z∼1. These exponents are consistent with a clean X-Y model in 2+1 dimensions.
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Affiliation(s)
- A Roy
- Department of Physics, Bar Ilan University, Ramat Gan 52900, Israel
| | - E Shimshoni
- Department of Physics, Bar Ilan University, Ramat Gan 52900, Israel
| | - A Frydman
- Department of Physics, Bar Ilan University, Ramat Gan 52900, Israel
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