1
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Almoalem A, Feldman I, Mangel I, Shlafman M, Yaish YE, Fischer MH, Moshe M, Ruhman J, Kanigel A. The observation of π-shifts in the Little-Parks effect in 4Hb-TaS 2. Nat Commun 2024; 15:4623. [PMID: 38816364 PMCID: PMC11139670 DOI: 10.1038/s41467-024-48260-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 04/23/2024] [Indexed: 06/01/2024] Open
Abstract
Finding evidence of non-trivial pairing states is one of the greatest experimental challenges in the field of unconventional superconductivity. Such evidence requires phase-sensitive probes susceptible to the internal structure of the order parameter. We report the measurement of the Little-Parks effect in the unconventional superconductor candidate 4Hb-TaS2. In half of our rings, which are fabricated from single-crystals, we find a π-shift in the transition-temperature oscillations. According to theory, such a π-shift is only possible if the order parameter is non-s-wave. In the absence of crystallographic defects, the shift provides evidence of a multi-component order parameter. Thus, this observation increases the likelihood of the two-component order parameter scenario in 4Hb-TaS2. Furthermore, we show that Tc is enhanced as a function of the out-of-plane field when a constant in-plane field is applied, which we explain using a two-component order-parameter.
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Affiliation(s)
- Avior Almoalem
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Irena Feldman
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Ilay Mangel
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel
| | - Michael Shlafman
- Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering, Technion, Haifa, 32000, Israel
| | - Yuval E Yaish
- Andrew and Erna Viterbi Faculty of Electrical and Computer Engineering, Technion, Haifa, 32000, Israel
| | - Mark H Fischer
- Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Michael Moshe
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Jonathan Ruhman
- Department of Physics, Bar-Ilan University, 52900, Ramat Gan, Israel
| | - Amit Kanigel
- Physics Department, Technion-Israel Institute of Technology, Haifa, 32000, Israel.
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2
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Levajac V, Barakov H, Mazur GP, van Loo N, Kouwenhoven LP, Nazarov YV, Wang JY. Supercurrent in the Presence of Direct Transmission and a Resonant Localized State. PHYSICAL REVIEW LETTERS 2024; 132:176304. [PMID: 38728734 DOI: 10.1103/physrevlett.132.176304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 01/25/2024] [Accepted: 04/02/2024] [Indexed: 05/12/2024]
Abstract
We study the current-phase relation (CPR) of an InSb-Al nanowire Josephson junction in parallel magnetic fields up to 700 mT. At high magnetic fields and in narrow voltage intervals of a gate under the junction, the CPR exhibits π shifts. The supercurrent declines within these gate intervals and shows asymmetric gate voltage dependence above and below them. We detect these features sometimes also at zero magnetic field. The observed CPR properties are reproduced by a theoretical model of supercurrent transport via interference between direct transmission and a resonant localized state.
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Affiliation(s)
- Vukan Levajac
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - Hristo Barakov
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - Grzegorz P Mazur
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - Nick van Loo
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - Leo P Kouwenhoven
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - Yuli V Nazarov
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - Ji-Yin Wang
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
- Beijing Academy of Quantum Information Sciences, 100193 Beijing, China
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3
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Debbarma R, Tsintzis A, Aspegren M, Souto RS, Lehmann S, Dick K, Leijnse M, Thelander C. Josephson Junction π-0 Transition Induced by Orbital Hybridization in a Double Quantum Dot. PHYSICAL REVIEW LETTERS 2023; 131:256001. [PMID: 38181374 DOI: 10.1103/physrevlett.131.256001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 11/20/2023] [Indexed: 01/07/2024]
Abstract
In this Letter, we manipulate the phase shift of a Josephson junction using a parallel double quantum dot (QD). By employing a superconducting quantum interference device, we determine how orbital hybridization and detuning affect the current-phase relation in the Coulomb blockade regime. For weak hybridization between the QDs, we find π junction characteristics if at least one QD has an unpaired electron. Notably the critical current is higher when both QDs have an odd electron occupation. By increasing the inter-QD hybridization the critical current is reduced, until eventually a π-0 transition occurs. A similar transition appears when detuning the QD levels at finite hybridization. Based on a zero-bandwidth model, we argue that both cases of phase-shift transitions can be understood considering an increased weight of states with a double occupancy in the ground state and with the Cooper pair transport dominated by local Andreev reflection.
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Affiliation(s)
- Rousan Debbarma
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
| | - Athanasios Tsintzis
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
| | - Markus Aspegren
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
| | - Rubén Seoane Souto
- Departamento de Física Teórica de la Materia Condensada, Condensed Matter Physics Center (IFIMAC) and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - Sebastian Lehmann
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
| | - Kimberly Dick
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
- Center for Analysis and Synthesis, Lund University, S-221 00 Lund, Sweden
| | - Martin Leijnse
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
| | - Claes Thelander
- Division of Solid State Physics and NanoLund, Lund University, S-221 00 Lund, Sweden
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4
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Bargerbos A, Pita-Vidal M, Žitko R, Splitthoff LJ, Grünhaupt L, Wesdorp JJ, Liu Y, Kouwenhoven LP, Aguado R, Andersen CK, Kou A, van Heck B. Spectroscopy of Spin-Split Andreev Levels in a Quantum Dot with Superconducting Leads. PHYSICAL REVIEW LETTERS 2023; 131:097001. [PMID: 37721843 DOI: 10.1103/physrevlett.131.097001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 07/27/2023] [Indexed: 09/20/2023]
Abstract
We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of a quantum dot Josephson junction tuned to be in a spin-1/2 ground state with an unpaired quasiparticle. Because of spin-orbit coupling, we resolve two flux-sensitive branches in the transmon spectrum, depending on the spin of the quasiparticle. A finite magnetic field shifts the two branches in energy, favoring one spin state and resulting in the anomalous Josephson effect. We demonstrate the excitation of the direct spin-flip transition using all-electrical control. Manipulation and control of the spin-flip transition enable the future implementation of charging energy protected Andreev spin qubits.
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Affiliation(s)
- Arno Bargerbos
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Marta Pita-Vidal
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Rok Žitko
- Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
| | - Lukas J Splitthoff
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Lukas Grünhaupt
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Jaap J Wesdorp
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Yu Liu
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Leo P Kouwenhoven
- QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Ramón Aguado
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain
| | | | - Angela Kou
- Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Bernard van Heck
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, Netherlands
- Dipartimento di Fisica, Università di Roma "La Sapienza", P.le Aldo Moro 5, 00185 Roma, Italy
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5
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Souto RS, Leijnse M, Schrade C. Josephson Diode Effect in Supercurrent Interferometers. PHYSICAL REVIEW LETTERS 2022; 129:267702. [PMID: 36608204 DOI: 10.1103/physrevlett.129.267702] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 10/10/2022] [Accepted: 12/02/2022] [Indexed: 06/17/2023]
Abstract
A Josephson diode is a nonreciprocal circuit element that supports a larger dissipationless supercurrent in one direction than in the other. In this Letter, we propose a class of Josephson diodes based on supercurrent interferometers composed of Andreev bound state Josephson junctions or interacting quantum dot Josephson junctions, which are not diodes themselves but possess nonsinusoidal current-phase relations. We show that such Josephson diodes have several important advantages, like being electrically tunable and requiring only time-reversal breaking by a magnetic flux. We also show that our diodes have a characteristic ac response, revealed by the Shapiro steps. Even the simplest realization of our Josephson diode paradigm that relies on only two junctions can achieve efficiencies of up to ∼40% and, interestingly, far greater efficiencies are achievable by concatenating interferometer loops. We hope that our Letter will stimulate the search for highly tunable Josephson diode effects in Josephson devices based semiconductor-superconductor hybrids, 2d materials, and topological insulators, where nonsinusoidal current-phase relations were recently observed.
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Affiliation(s)
- Rubén Seoane Souto
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Division of Solid State Physics and NanoLund, Lund University, S-22100 Lund, Sweden
| | - Martin Leijnse
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Division of Solid State Physics and NanoLund, Lund University, S-22100 Lund, Sweden
| | - Constantin Schrade
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
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6
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Lee M, López R, Xu HQ, Platero G. Proposal for Detection of the 0^{'} and π^{'} Phases in Quantum-Dot Josephson Junctions. PHYSICAL REVIEW LETTERS 2022; 129:207701. [PMID: 36462010 DOI: 10.1103/physrevlett.129.207701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 10/03/2022] [Indexed: 06/17/2023]
Abstract
The competition between the Kondo correlation and superconductivity in quantum-dot Josephson junctions (QDJJs) has been known to drive a quantum phase transition between 0 and π junctions. Theoretical studies so far have predicted that under strong Coulomb correlations the 0-π transition should go through intermediate states, 0^{'} and π^{'} phases. By combining a nonperturbative numerical method and the resistively shunted junction model, we investigated the magnetic-field-driven phase transition of the QDJJs in the Kondo regime and found that the low-field magnetotransport exhibits a unique feature which can be used to distinguish the intermediate phases. In particular, the magnetic-field driven π^{'}-π transition is found to lead to the enhancement of the supercurrent which is strongly related to the Kondo effect.
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Affiliation(s)
- Minchul Lee
- Department of Applied Physics and Institute of Natural Science, College of Applied Science, Kyung Hee University, Yongin 17104, Korea
| | - Rosa López
- Institut de Física Interdisciplinària i de Sistemes Complexos IFISC (CSIC-UIB), E-07122 Palma de Mallorca, Spain
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Gloria Platero
- Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), 28049 Cantoblanco, Madrid, Spain
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7
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Microstructure and Anisotropic Order Parameter of Boron-Doped Nanocrystalline Diamond Films. CRYSTALS 2022. [DOI: 10.3390/cryst12081031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Unconventional superconductivity in heavily boron-doped nanocrystalline diamond films (HBDDF) produced a significant amount of interest. However, the exact pairing mechanism has not been understood due to a lack of understanding of crystal symmetry, which is broken at the grain boundaries. The superconducting order parameter (Δ) of HBDDF is believed to be anisotropic since boron atoms form a complex structure with carbon and introduce spin-orbit coupling to the diamond system. From ultra-high resolution transmission electron microscopy, the internal symmetry of the grain boundary structure of HBDDF is revealed, which can explain these films’ unconventional superconducting transport features. Here, we show the signature of the anisotropic Δ in HBDDF by breaking the structural symmetry in a layered microstructure, enabling a Rashba-type spin-orbit coupling. The superlattice-like structure in diamond describes a modulation that explains strong insulator peak features observed in temperature-dependent resistance, a transition of the magnetic field-dependent resistance, and their oscillatory, as well as angle-dependent, features. Overall, the interface states of the diamond films can be explained by the well-known Shockley model describing the layers connected by vortex-like structures, hence forming a topologically protected system.
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8
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Wang JY, Schrade C, Levajac V, van Driel D, Li K, Gazibegovic S, Badawy G, Op het Veld RLM, Lee JS, Pendharkar M, Dempsey CP, Palmstrøm CJ, Bakkers EPAM, Fu L, Kouwenhoven LP, Shen J. Supercurrent parity meter in a nanowire Cooper pair transistor. SCIENCE ADVANCES 2022; 8:eabm9896. [PMID: 35452283 PMCID: PMC9032955 DOI: 10.1126/sciadv.abm9896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
We study a Cooper pair transistor realized by two Josephson weak links that enclose a superconducting island in an InSb-Al hybrid nanowire. When the nanowire is subject to a magnetic field, isolated subgap levels arise in the superconducting island and, because of the Coulomb blockade, mediate a supercurrent by coherent cotunneling of Cooper pairs. We show that the supercurrent resulting from such cotunneling events exhibits, for low to moderate magnetic fields, a phase offset that discriminates even and odd charge ground states on the superconducting island. Notably, this phase offset persists when a subgap state approaches zero energy and, based on theoretical considerations, permits parity measurements of subgap states by supercurrent interferometry. Such supercurrent parity measurements could, in a series of experiments, provide an alternative approach for manipulating and protecting quantum information stored in the isolated subgap levels of superconducting islands.
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Affiliation(s)
- Ji-Yin Wang
- QuTech and Kavli Institute of NanoScience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Constantin Schrade
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Vukan Levajac
- QuTech and Kavli Institute of NanoScience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - David van Driel
- QuTech and Kavli Institute of NanoScience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Kongyi Li
- QuTech and Kavli Institute of NanoScience, Delft University of Technology, 2600 GA Delft, Netherlands
| | - Sasa Gazibegovic
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Ghada Badawy
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Roy L. M. Op het Veld
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Joon Sue Lee
- California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mihir Pendharkar
- Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Connor P. Dempsey
- Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Chris J. Palmstrøm
- California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
- Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
- Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Erik P. A. M. Bakkers
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Leo P. Kouwenhoven
- QuTech and Kavli Institute of NanoScience, Delft University of Technology, 2600 GA Delft, Netherlands
- Microsoft Quantum Lab Delft, 2600 GA Delft, Netherlands
| | - Jie Shen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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9
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de Mello EVL. The charge-density-wave signature on the superfluid density of cuprate superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:145503. [PMID: 33395674 DOI: 10.1088/1361-648x/abd812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 01/04/2021] [Indexed: 06/12/2023]
Abstract
The superfluid density or superconducting (SC) carrier concentrationnscof cuprates has been the subject of intense investigations but there is not any single theory capable to explain all the available data. Here we show that the behavior ofnscin under and overdoped cuprates are a consequence of an SC interaction based on charge fluctuations in the incommensurate charge-density-waves (CDW) domains. We have shown that this interaction scales with the CDW amplitude or the pseudogap (PG) energy, yielding local SC amplitudes and Josephson currents. The average Josephson energyEJis proportional to the phase stiffness or superfluid densityρsc∝nsc. We find thatnsc(p) increases almost linearly with dopingpin the underdoped region and in the charge abundant overdoped only a few fractions of the holes condense leading to two kinds of carriers, a recently confirmed feature. The calculations and theρscdata uncover how the PG-CDW-SC intertwined orders operate to yield cuprates properties.
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Affiliation(s)
- E V L de Mello
- Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ, Brazil
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10
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Razmadze D, O'Farrell ECT, Krogstrup P, Marcus CM. Quantum Dot Parity Effects in Trivial and Topological Josephson Junctions. PHYSICAL REVIEW LETTERS 2020; 125:116803. [PMID: 32975997 DOI: 10.1103/physrevlett.125.116803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
An odd-occupied quantum dot in a Josephson junction can flip transmission phase, creating a π junction. When the junction couples topological superconductors, no phase flip is expected. We investigate this and related effects in a full-shell hybrid interferometer, using gate voltage to control dot-junction parity and axial magnetic flux to control the transition from trivial to topological superconductivity. Enhanced zero-bias conductance and critical current for odd parity in the topological phase reflects hybridization of the confined spin with zero-energy modes in the leads.
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Affiliation(s)
- D Razmadze
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Lab-Copenhagen, 2100 Copenhagen, Denmark
| | - E C T O'Farrell
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Lab-Copenhagen, 2100 Copenhagen, Denmark
| | - P Krogstrup
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Materials Lab-Copenhagen, 2800 Kongens Lyngby, Denmark
| | - C M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Lab-Copenhagen, 2100 Copenhagen, Denmark
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11
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de Mello EVL. Calculations of quantum oscillations in cuprate superconductors considering the pseudogap. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:38LT01. [PMID: 32422616 DOI: 10.1088/1361-648x/ab9407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
The observations of quantum oscillations frequencies in overdoped cuprates were in agreement with a charge density contained in a cylindrical Fermi surface but the measured frequencies of underdoped compounds were much smaller than expected. This was attributed to a topological transition into small pockets of Fermi surface associated with the existence of charge density waves. On the other hand, spectroscopic measurements suggested that the large two-dimensional Fermi surface changes continuously into a set of four disconnected arcs. Here we take into account the effect of the pseudogap that limits the availablek-space area where the Landau levels are developed on the Luttinger theorem and obtain the correct total carrier densities. The calculations show how the disconnected arcs evolve into a closed Fermi surface reconciling the experiments.
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Affiliation(s)
- E V L de Mello
- Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ, Brazil
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12
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Meden V. The Anderson-Josephson quantum dot-a theory perspective. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:163001. [PMID: 30630142 DOI: 10.1088/1361-648x/aafd6a] [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
Recent progress in nanoscale manufacturing has allowed to experimentally investigate quantum dots coupled to two superconducting leads in controlled and tunable setups. The equilibrium Josephson current was measured in on-chip superconducting quantum interference devices, and subgap states were investigated using weakly coupled metallic leads for spectroscopy. This has reinstated two 'classic' problems on the agenda of theoretical condensed matter physics: (1) the Josephson effect and (2) quantum spins in superconductors. The relevance of the former is obvious as the barrier, which separates the two superconductors in a standard Josephson junction, is merely replaced by the quantum dot with well separated energy levels. For odd filling of the dot it acts as a quantum mechanical spin-1/2 and thereby the relevance of the latter becomes apparent also. For normal conducting leads and at odd dot filling the Kondo effect strongly modifies the transport properties as can, e.g. be studied within the Anderson model. One can expect the same for superconducting leads, and in certain parameter regimes remnants of Kondo physics, i.e. strong electronic correlations, will affect the Josephson current. In this topical review, we discuss the status of the theoretical understanding of the Anderson-Josephson quantum dot in equilibrium, mainly focusing on the Josephson current. We introduce a minimal model consisting of a dot which can only host a single spin-up and a single spin-down electron repelling each other by a local Coulomb interaction. The dot is tunnel-coupled to two superconducting leads as described by the Bardeen-Cooper-Schrieffer Hamiltonian. This model was investigated using a variety of methods, some capturing aspects of Kondo physics, while others failing in this respect. We briefly review this. The model shows a first order level-crossing quantum phase transition when varying any parameter, provided that the others are within appropriate ranges. At vanishing temperature it leads to a jump of the Josephson current. To study the qualitative behavior of the phase diagram, or the Josephson current, several of the methods can be used. However, for a quantitative description, elaborate quantum many-body methods must be employed. We show that a quantitative agreement between accurate results obtained for the simple model and measurements of the current can be reached. This confirms that the experiments reveal the finite temperature signatures of the zero temperature transition. In addition, we consider two examples of more complex dot geometries, which might be experimentally realized in the near future. The first is characterized by the interplay of the above level-crossing physics and the Fano effect, and the second by the interplay of superconductivity and almost degenerate singlet and triplet two-body states.
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Affiliation(s)
- V Meden
- Institut für Theorie der Statistischen Physik, RWTH Aachen University and JARA-Fundamentals of Future Information Technology, 52056 Aachen, Germany
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13
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Volpez Y, Loss D, Klinovaja J. Second-Order Topological Superconductivity in π-Junction Rashba Layers. PHYSICAL REVIEW LETTERS 2019; 122:126402. [PMID: 30978045 DOI: 10.1103/physrevlett.122.126402] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Indexed: 06/09/2023]
Abstract
We consider a Josephson junction bilayer consisting of two tunnel-coupled two-dimensional electron gas layers with Rashba spin-orbit interaction, proximitized by a top and bottom s-wave superconductor with phase difference ϕ close to π. We show that, in the presence of a finite weak in-plane Zeeman field, the bilayer can be driven into a second order topological superconducting phase, hosting two Majorana corner states (MCSs). If ϕ=π, in a rectangular geometry, these zero-energy bound states are located at two opposite corners determined by the direction of the Zeeman field. If the phase difference ϕ deviates from π by a critical value, one of the two MCSs gets relocated to an adjacent corner. As the phase difference ϕ increases further, the system becomes trivially gapped. The obtained MCSs are robust against static and magnetic disorder. We propose two setups that could realize such a model: one is based on controlling ϕ by magnetic flux, the other involves an additional layer of randomly oriented magnetic impurities responsible for the phase shift of π in the proximity-induced superconducting pairing.
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Affiliation(s)
- Yanick Volpez
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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14
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Camjayi A, Arrachea L, Aligia A, von Oppen F. Fractional Spin and Josephson Effect in Time-Reversal-Invariant Topological Superconductors. PHYSICAL REVIEW LETTERS 2017; 119:046801. [PMID: 29341741 DOI: 10.1103/physrevlett.119.046801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Indexed: 06/07/2023]
Abstract
Time-reversal-invariant topological superconducting (TRITOPS) wires are known to host a fractional spin ℏ/4 at their ends. We investigate how this fractional spin affects the Josephson current in a TRITOPS-quantum dot-TRITOPS Josephson junction, describing the wire in a model that can be tuned between a topological and a nontopological phase. We compute the equilibrium Josephson current of the full model by continuous-time Monte Carlo simulations and interpret the results within an effective low-energy theory. We show that in the topological phase, the 0-to-π transition is quenched via formation of a spin singlet from the quantum-dot spin and the fractional spins associated with the two adjacent topological superconductors.
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Affiliation(s)
- Alberto Camjayi
- Departamento de Física, FCEyN, Universidad de Buenos Aires and IFIBA, Pabellón I, Ciudad Universitaria, 1428 CABA, Argentina
| | - Liliana Arrachea
- International Center for Advanced Studies, ECyT-UNSAM, Campus Miguelete, 25 de Mayo y Francia, 1650 Buenos Aires, Argentina
| | - Armando Aligia
- Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 S. C. de Bariloche, Argentina
| | - Felix von Oppen
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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Shekhter RI, Entin-Wohlman O, Jonson M, Aharony A. Rashba Splitting of Cooper Pairs. PHYSICAL REVIEW LETTERS 2016; 116:217001. [PMID: 27284669 DOI: 10.1103/physrevlett.116.217001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Indexed: 06/06/2023]
Abstract
We investigate theoretically the properties of a weak link between two superconducting leads, which has the form of a nonsuperconducting nanowire with a strong Rashba spin-orbit coupling caused by an electric field. In the Coulomb-blockade regime of single-electron tunneling, we find that such a weak link acts as a "spin splitter" of the spin states of Cooper pairs tunneling through the link, to an extent that depends on the direction of the electric field. We show that the Josephson current is sensitive to interference between the resulting two transmission channels, one where the spins of both members of a Cooper pair are preserved and one where they are both flipped. As a result, the current is a periodic function of the strength of the spin-orbit interaction and of the bending angle of the nanowire (when mechanically bent); an identical effect appears due to strain-induced spin-orbit coupling. In contrast, no spin-orbit induced interference effect can influence the current through a single weak link connecting two normal metals.
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Affiliation(s)
- R I Shekhter
- Department of Physics, University of Gothenburg, SE-412 96 Göteborg, Sweden
| | - O Entin-Wohlman
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
- Physics Department, Ben Gurion University, Beer Sheva 84105, Israel
| | - M Jonson
- Department of Physics, University of Gothenburg, SE-412 96 Göteborg, Sweden
- SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
| | - A Aharony
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
- Physics Department, Ben Gurion University, Beer Sheva 84105, Israel
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16
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Wang L, Xu C, Liu Z, Chen L, Ma X, Cheng HM, Ren W, Kang N. Magnetotransport Properties in High-Quality Ultrathin Two-Dimensional Superconducting Mo2C Crystals. ACS NANO 2016; 10:4504-4510. [PMID: 27065100 DOI: 10.1021/acsnano.6b00270] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Ultrathin transition metal carbides are a class of developing two-dimensional (2D) materials with superconductivity and show great potentials for electrical energy storage and other applications. Here, we report low-temperature magnetotransport measurements on high-quality ultrathin 2D superconducting α-Mo2C crystals synthesized by a chemical vapor deposition method. The magnetoresistance curves exhibit reproducible oscillations at low magnetic fields for temperature far below the superconducting transition temperature of the crystals. We interpret the oscillatory magnetoresistance as a consequence of screening currents circling around the boundary of triangle-shaped terraces found on the surface of ultrathin Mo2C crystals. As the sample thickness decreases, the Mo2C crystals exhibit negative magnetoresistance deep in the superconducting transition regime, which reveals strong phase fluctuations of the superconducting order parameters associated with the superconductor-insulator transition. Our results demonstrate that the ultrathin superconducting Mo2C crystals provide an interesting system for studying rich transport phenomena in a 2D crystalline superconductor with enhanced quantum fluctuations.
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Affiliation(s)
- Libin Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University , Beijing 100871, China
| | - Chuan Xu
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Zhibo Liu
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Long Chen
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Xiuliang Ma
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Hui-Ming Cheng
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Wencai Ren
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Ning Kang
- Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University , Beijing 100871, China
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17
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Schrade C, Zyuzin AA, Klinovaja J, Loss D. Proximity-Induced π Josephson Junctions in Topological Insulators and Kramers Pairs of Majorana Fermions. PHYSICAL REVIEW LETTERS 2015; 115:237001. [PMID: 26684136 DOI: 10.1103/physrevlett.115.237001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Indexed: 06/05/2023]
Abstract
We study two microscopic models of topological insulators in contact with an s-wave superconductor. In the first model the superconductor and the topological insulator are tunnel coupled via a layer of randomly distributed scalar and of randomly oriented spin impurities. Here, we demonstrate that spin-flip tunneling dominates over the spin-conserving one. In the second model the tunnel coupling is realized by a spatially nonuniform array of single-level quantum dots with randomly oriented spins. We find that the tunnel region forms a π junction where the effective order parameter changes sign. Because of the random spin orientation, effectively both models exhibit time-reversal symmetry. The proposed π junctions support topological superconductivity without magnetic fields and can be used to generate and manipulate Kramers pairs of Majorana fermions by gates.
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Affiliation(s)
- Constantin Schrade
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - A A Zyuzin
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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18
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Shekhter RI, Entin-Wohlman O, Aharony A. Suspended nanowires as mechanically controlled Rashba spin splitters. PHYSICAL REVIEW LETTERS 2013; 111:176602. [PMID: 24206510 DOI: 10.1103/physrevlett.111.176602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Indexed: 06/02/2023]
Abstract
Suspended nanowires are shown to provide mechanically controlled coherent mixing or splitting of the spin states of transmitted electrons, caused by the Rashba spin-orbit interaction. The sensitivity of the latter to mechanical bending makes the wire a tunable nanoelectromechanical weak link between reservoirs. When the reservoirs are populated with misbalanced "spin-up and spin-down" electrons, the wire becomes a source of split spin currents, which are not associated with electric charge transfer and which do not depend on temperature or driving voltages. The mechanical vibrations of the bended wires allow for additional tunability of these splitters by applying a magnetic field and varying the temperature. Clean metallic carbon nanotubes of a few microns length are good candidates for generating spin conductance of the same order as the charge conductance (divided by e(2)) which would have been induced by electric driving voltages.
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Affiliation(s)
- R I Shekhter
- Department of Physics, Göteborg University, SE-412 96 Göteborg, Sweden
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Chang W, Manucharyan VE, Jespersen TS, Nygård J, Marcus CM. Tunneling spectroscopy of quasiparticle bound states in a spinful Josephson junction. PHYSICAL REVIEW LETTERS 2013; 110:217005. [PMID: 23745916 DOI: 10.1103/physrevlett.110.217005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Indexed: 06/02/2023]
Abstract
The spectrum of a segment of InAs nanowire, confined between two superconducting leads, was measured as function of gate voltage and superconducting phase difference using a third normal-metal tunnel probe. Subgap resonances for odd electron occupancy-interpreted as bound states involving a confined electron and a quasiparticle from the superconducting leads, reminiscent of Yu-Shiba-Rusinov states-evolve into Kondo-related resonances at higher magnetic fields. An additional zero-bias peak of unknown origin is observed to coexist with the quasiparticle bound states.
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Affiliation(s)
- W Chang
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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20
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Kim BK, Ahn YH, Kim JJ, Choi MS, Bae MH, Kang K, Lim JS, López R, Kim N. Transport measurement of Andreev bound states in a Kondo-correlated quantum dot. PHYSICAL REVIEW LETTERS 2013; 110:076803. [PMID: 25166391 DOI: 10.1103/physrevlett.110.076803] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Indexed: 06/03/2023]
Abstract
We report nonequilibrium transport measurements of gate-tunable Andreev bound states in a carbon nanotube quantum dot coupled to two superconducting leads. In particular, we observe clear features of two types of Kondo ridges, which can be understood in terms of the interplay between the Kondo effect and superconductivity. In the first type (type I), the coupling is strong and the Kondo effect is dominant. Levels of the Andreev bound states display anticrossing in the middle of the ridge. On the other hand, crossing of the two Andreev bound states is shown in the second type (type II) together with the 0-π transition of the Josephson junction. Our scenario is well understood in terms of only a single dimensionless parameter, k(B)T(K)(min)/Δ, where T(K)(min) and Δ are the minimum Kondo temperature of a ridge and the superconducting order parameter, respectively. Our observation is consistent with measurements of the critical current, and is supported by numerical renormalization group calculations.
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Affiliation(s)
- Bum-Kyu Kim
- Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea and Department of Physics, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Ye-Hwan Ahn
- Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea and Department of Physics, Korea University, Seoul 136-713, Republic of Korea
| | - Ju-Jin Kim
- Department of Physics, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Mahn-Soo Choi
- Department of Physics, Korea University, Seoul 136-713, Republic of Korea
| | - Myung-Ho Bae
- Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea
| | - Kicheon Kang
- Department of Physics, Chonnam National University, Gwangju 500-757, Republic of Korea
| | - Jong Soo Lim
- Institut de Física Interdisciplinar i de Sistemes Complexos IFISC (CSIC-UIB), E-07122 Palma de Mallorca, Spain
| | - Rosa López
- Institut de Física Interdisciplinar i de Sistemes Complexos IFISC (CSIC-UIB), E-07122 Palma de Mallorca, Spain and Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain
| | - Nam Kim
- Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea
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Droste S, Andergassen S, Splettstoesser J. Josephson current through interacting double quantum dots with spin-orbit coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:415301. [PMID: 23006317 DOI: 10.1088/0953-8984/24/41/415301] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We study the effect of Rashba spin-orbit interaction on the Josephson current through a double quantum dot in the presence of Coulomb repulsion. In particular, we describe the characteristic effects on the magnetic field-induced singlet-triplet transition in the molecular regime. Exploring the whole parameter space, we analyze the effects of the device asymmetry, the orientation of the applied magnetic field with respect to the spin-orbit interaction, and finite temperatures. We find that at finite temperatures the orthogonal component of the spin-orbit interaction exhibits a similar effect to the Coulomb interaction inducing the occurrence of a π-phase at particle-hole symmetry. This provides a new route to the experimental observability of the π-phase in multi-level quantum dots.
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Affiliation(s)
- Stephanie Droste
- Institut für Theorie der Statistischen Physik, RWTH Aachen University, 52056 Aachen, Germany.
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22
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Lim JS, López R, Aguado R. Josephson current in carbon nanotubes with spin-orbit interaction. PHYSICAL REVIEW LETTERS 2011; 107:196801. [PMID: 22181630 DOI: 10.1103/physrevlett.107.196801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Indexed: 05/31/2023]
Abstract
We demonstrate that curvature-induced spin-orbit coupling induces a 0-π transition in the Josephson current through a carbon nanotube quantum dot coupled to superconducting leads. In the noninteracting regime, the transition can be tuned by applying a parallel magnetic field near the critical field where orbital states become degenerate. Moreover, the interplay between charging and spin-orbit effects in the Coulomb blockade and cotunneling regimes leads to a rich phase diagram with well-defined (analytical) boundaries in parameter space. Finally, the 0 phase always prevails in the Kondo regime. Our calculations are relevant in view of recent experimental advances in transport through ultraclean carbon nanotubes.
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Affiliation(s)
- Jong Soo Lim
- Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain
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23
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Laflorencie N, Mila F. Condensate-free superfluid induced by the frustrated proximity effect. PHYSICAL REVIEW LETTERS 2011; 107:037203. [PMID: 21838398 DOI: 10.1103/physrevlett.107.037203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 04/29/2011] [Indexed: 05/31/2023]
Abstract
Since the discovery of superfluidity in 4He and Landau's phenomenological theory, the relationship between Bose condensation and superfluidity has been intensely debated. 4He is known by now to be both superfluid and condensed at low temperature, and more generally, in dimension D≥2, all superfluid bosonic models realized in experiments are condensed in their ground state, the most recent example being provided by ultracold bosonic atoms trapped in an optical lattice. In this Letter, it is shown that a 2D gas of bosons which is not condensed at T=0 can be achieved by populating a layer through a frustrated proximity effect from a superfluid reservoir. This condensate-free bosonic fluid is further shown to be a superfluid with incommensurate correlations.
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Affiliation(s)
- Nicolas Laflorencie
- Laboratoire de Physique des Solides, Université Paris-Sud, UMR-8502 CNRS, 91405 Orsay, France
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24
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De Franceschi S, Kouwenhoven L, Schönenberger C, Wernsdorfer W. Hybrid superconductor-quantum dot devices. NATURE NANOTECHNOLOGY 2010; 5:703-711. [PMID: 20852639 DOI: 10.1038/nnano.2010.173] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Advances in nanofabrication techniques have made it possible to make devices in which superconducting electrodes are connected to non-superconducting nanostructures such as quantum dots. The properties of these hybrid devices result from a combination of a macroscopic quantum phenomenon involving large numbers of electrons (superconductivity) and the ability to control single electrons, offered by quantum dots. Here we review research into electron transport and other fundamental processes that have been studied in these devices. We also describe potential applications, such as a transistor in which the direction of a supercurrent can be reversed by adding just one electron to a quantum dot.
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Affiliation(s)
- Silvano De Franceschi
- SPSMS/LaTEQS, CEA-INAC/UJF-Grenoble 1, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France.
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25
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Zitko R, Lee M, López R, Aguado R, Choi MS. Josephson current in strongly correlated double quantum dots. PHYSICAL REVIEW LETTERS 2010; 105:116803. [PMID: 20867595 DOI: 10.1103/physrevlett.105.116803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Indexed: 05/29/2023]
Abstract
We study the Josephson current through a serial double quantum dot and the associated 0-π transitions which result from the subtle interplay between the superconductivity, the Kondo physics, and the interdot superexchange interaction. The competition between them is examined by tuning the relative strength Δ/T(K) of the superconducting gap and the Kondo temperature, for different strengths of the superexchange coupling determined by the interdot tunneling t relative to the level broadening Γ. We find strong renormalization of t, a significant role of the superexchange coupling J, and a rich phase diagram of the 0 and π-junction regimes. In particular, when both the superconductivity and the exchange interaction compete with the Kondo physics (Δ∼J∼T(K)), there appears an island of π' phase at large values of the superconducting phase difference.
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Affiliation(s)
- Rok Zitko
- J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
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26
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Zazunov A, Egger R, Jonckheere T, Martin T. Anomalous Josephson current through a spin-orbit coupled quantum dot. PHYSICAL REVIEW LETTERS 2009; 103:147004. [PMID: 19905596 DOI: 10.1103/physrevlett.103.147004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Indexed: 05/28/2023]
Abstract
For a general model of a mesoscopic multilevel quantum dot, we determine the necessary conditions for the existence of an anomalous Josephson current with spontaneously broken time-reversal symmetry. They correspond to a finite spin-orbit coupling, a suitably oriented Zeeman field, and the dot being a chiral conductor. We provide analytical expressions for the anomalous supercurrent covering a wide parameter regime.
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Affiliation(s)
- A Zazunov
- Institut für Theoretische Physik, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
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27
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Lee M, Jonckheere T, Martin T. Josephson effect through an isotropic magnetic molecule. PHYSICAL REVIEW LETTERS 2008; 101:146804. [PMID: 18851557 DOI: 10.1103/physrevlett.101.146804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Indexed: 05/26/2023]
Abstract
We study the Josephson effect through a quantum dot magnet whose spin is isotropic and which is coupled to the dot electron spin via exchange coupling. We calculate the Andreev levels and the supercurrent and examine the intertwined effect of the exchange coupling, Kondo correlation, and superconductivity. The former suppresses Kondo correlations, which triggers phase transitions from the 0 to the pi state, but strong antiferromagnetic coupling restores the 0 state. The asymmetric phase diagram in the exchange coupling suggests that the coupling sign could be determined in experiments.
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Affiliation(s)
- Minchul Lee
- Centre de Physique Théorique, UMR6207, Case 907, Luminy, 13288 Marseille Cedex 9, France
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28
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Berg E, Fradkin E, Kim EA, Kivelson SA, Oganesyan V, Tranquada JM, Zhang SC. Dynamical layer decoupling in a stripe-ordered high-T(c) superconductor. PHYSICAL REVIEW LETTERS 2007; 99:127003. [PMID: 17930544 DOI: 10.1103/physrevlett.99.127003] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Indexed: 05/25/2023]
Abstract
In the stripe-ordered state of a strongly correlated two-dimensional electronic system, under a set of special circumstances, the superconducting condensate, like the magnetic order, can occur at a nonzero wave vector corresponding to a spatial period double that of the charge order. In this case, the Josephson coupling between near neighbor planes, especially in a crystal with the special structure of La(2-x)Ba(x)CuO(4), vanishes identically. We propose that this is the underlying cause of the dynamical decoupling of the layers recently observed in transport measurements at x = 1/8.
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Affiliation(s)
- E Berg
- Department of Physics, Stanford University, Stanford, California 94305-4060, USA
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29
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Jørgensen HI, Novotný T, Grove-Rasmussen K, Flensberg K, Lindelof PE. Critical current 0-pi transition in designed Josephson Quantum Dot junctions. NANO LETTERS 2007; 7:2441-5. [PMID: 17637018 DOI: 10.1021/nl071152w] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We report on quantum dot based Josephson junctions designed specifically for measuring the supercurrent. From high-accuracy fitting of the current-voltage characteristics, we determine the full magnitude of the supercurrent (critical current). Strong gate modulation of the critical current is observed through several consecutive Coulomb blockade oscillations. The critical current crosses zero close to, but not at, resonance due to the so-called 0-pi transition in agreement with a simple theoretical model.
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Affiliation(s)
- H Ingerslev Jørgensen
- Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
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30
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van Dam JA, Nazarov YV, Bakkers EPAM, De Franceschi S, Kouwenhoven LP. Supercurrent reversal in quantum dots. Nature 2006; 442:667-70. [PMID: 16900196 DOI: 10.1038/nature05018] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 06/22/2006] [Indexed: 11/08/2022]
Abstract
When two superconductors are electrically connected by a weak link--such as a tunnel barrier--a zero-resistance supercurrent can flow. This supercurrent is carried by Cooper pairs of electrons with a combined charge of twice the elementary charge, e. The 2e charge quantum is clearly visible in the height of voltage steps in Josephson junctions under microwave irradiation, and in the magnetic flux periodicity of h/2e (where h is Planck's constant) in superconducting quantum interference devices. Here we study supercurrents through a quantum dot created in a semiconductor nanowire by local electrostatic gating. Owing to strong Coulomb interaction, electrons only tunnel one-by-one through the discrete energy levels of the quantum dot. This nevertheless can yield a supercurrent when subsequent tunnel events are coherent. These quantum coherent tunnelling processes can result in either a positive or a negative supercurrent, that is, in a normal or a pi-junction, respectively. We demonstrate that the supercurrent reverses sign by adding a single electron spin to the quantum dot. When excited states of the quantum dot are involved in transport, the supercurrent sign also depends on the character of the orbital wavefunctions.
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Affiliation(s)
- Jorden A van Dam
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA, Delft, The Netherlands
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31
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Andersen BM, Bobkova IV, Hirschfeld PJ, Barash YS. 0-pi transitions in Josephson junctions with antiferromagnetic interlayers. PHYSICAL REVIEW LETTERS 2006; 96:117005. [PMID: 16605855 DOI: 10.1103/physrevlett.96.117005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Indexed: 05/08/2023]
Abstract
We show that the dc Josephson current through superconductor-antiferromagnet-superconductor (S-AF-S) junctions manifests a remarkable atomic-scale dependence on the interlayer thickness. At low temperatures the junction is either a 0 or pi junction depending on whether the AF interlayer consists of an even or odd number of atomic layers. This is associated with different symmetries of the AF interlayers in the two cases. In the junction with odd AF interlayers an additional pi- 0 transition can take place as a function of temperature. This originates from the interplay of spin-split Andreev bound states. Experimental implications of these theoretical findings are discussed.
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Affiliation(s)
- Brian M Andersen
- Department of Physics, University of Florida, Gainesville, Florida 32611-8440, USA
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32
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Le Hur K, Recher P, Dupont E, Loss D. Mesoscopic resonating valence bond system on a triple dot. PHYSICAL REVIEW LETTERS 2006; 96:106803. [PMID: 16605773 DOI: 10.1103/physrevlett.96.106803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2005] [Indexed: 05/08/2023]
Abstract
We theoretically introduce a mesoscopic pendulum from a triple dot. The pendulum is fastened through a singly occupied dot (spin qubit). Two other strongly capacitively coupled islands form a double-dot charge qubit with one electron in excess oscillating between the two low-energy charge states (1,0) and (0,1). The triple dot is placed between two superconducting leads. Under realistic conditions, the main proximity effect stems from the injection of resonating singlet (valence) bonds on the triple dot. This gives rise to a Josephson current that is charge- and spin-dependent and, as a consequence, exhibits a distinct resonance as a function of the superconducting phase difference.
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Affiliation(s)
- Karyn Le Hur
- Département de Physique et RQMP, Université de Sherbrooke, Sherbrooke, Québec, Canada, J1K 2R1
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33
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Mori M, Maekawa S. Effect of antiferromagnetic planes on the superconducting properties of multilayered high-Tc cuprates. PHYSICAL REVIEW LETTERS 2005; 94:137003. [PMID: 15904020 DOI: 10.1103/physrevlett.94.137003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2004] [Indexed: 05/02/2023]
Abstract
We propose a mechanism for high critical temperature (T(c)) in the coexistent phase of superconducting (SC) and antiferromagnetic (AFM) CuO2 planes in multilayered cuprates. The Josephson coupling between the SC planes separated by an AFM insulator (Mott insulator) is calculated perturbatively up to the fourth order in terms of the hopping integral between adjacent CuO2 planes. It is shown that the AFM exchange splitting in the AFM plane suppresses the so-called pi-Josephson coupling, and the long-ranged 0-Josephson coupling leads to coexistence with a rather high value of T(c).
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Affiliation(s)
- M Mori
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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Siano F, Egger R. Josephson current through a nanoscale magnetic quantum dot. PHYSICAL REVIEW LETTERS 2004; 93:047002. [PMID: 15323785 DOI: 10.1103/physrevlett.93.047002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Indexed: 05/24/2023]
Abstract
We present theoretical results for the equilibrium Josephson current through an Anderson dot tuned into the magnetic regime, using Hirsch-Fye Monte Carlo simulations covering the complete crossover from Kondo-dominated physics to pi junction behavior in a numerically exact way. Within the "magnetic" regime, U/Gamma >> 1 and epsilon0/Gamma < or = 1, the Josephson current is found to depend only on Delta/TK, where Delta is the BCS gap and TK the Kondo temperature. The junction behavior can be classified into four different quantum phases. We describe these behaviors, specify the associated three transition points, and identify a local minimum in the critical current of the junction as a function of Delta/TK.
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Affiliation(s)
- F Siano
- Institut für Theoretische Physik, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
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Yeyati AL, Martín-Rodero A, Vecino E. Nonequilibrium dynamics of Andreev states in the Kondo regime. PHYSICAL REVIEW LETTERS 2003; 91:266802. [PMID: 14754078 DOI: 10.1103/physrevlett.91.266802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2003] [Indexed: 05/24/2023]
Abstract
The transport properties of a quantum dot coupled to superconducting leads are analyzed. It is shown that the quasiparticle current in the Kondo regime is determined by the nonequilibrium dynamics of subgap states (Andreev states) under an applied voltage. The current at low bias is suppressed exponentially for decreasing Kondo temperature in agreement with recent experiments. We also predict novel interference effects due to multiple Landau-Zener transitions between Andreev states.
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Affiliation(s)
- A Levy Yeyati
- Departamento de Física Teórica de la Materia Condensada CV, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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Abstract
The conventional theory of metals is in crisis. In the past 15 years, there has been an unexpected sprouting of metallic states in low-dimensional systems, directly contradicting conventional wisdom. For example, bosons are thought to exist in one of two ground states: condensed in a superconductor or localized in an insulator. However, several experiments on thin metal-alloy films have observed that a metallic phase disrupts the direct transition between the superconductor and the insulator. We analyze the experiments on the insulator-superconductor transition and argue that the intervening metallic phase is bosonic. All relevant theoretical proposals for the Bose metal are discussed, particularly the recent idea that the metallic phase is glassy. The implications for the putative vortex-glass state in the copper oxide superconductors are examined.
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Affiliation(s)
- Philip Phillips
- Loomis Laboratory of Physics, University of Illinois at Urbana-Champaign, 1100 West Green Street, Urbana, IL 61801-3080, USA.
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Dalidovich D, Phillips P. Phase glass is a Bose metal: a new conducting state in two dimensions. PHYSICAL REVIEW LETTERS 2002; 89:027001. [PMID: 12097011 DOI: 10.1103/physrevlett.89.027001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2001] [Indexed: 05/23/2023]
Abstract
In the quantum rotor model with random exchange interactions having a nonzero mean, three phases, a (i) phase (Bose) glass, (ii) superfluid, and (iii) Mott insulator, meet at a bicritical point. We demonstrate that proximity to the bicritical point and the coupling between the energy landscape and the dissipative degrees of freedom of the phase glass lead to a metallic state at T = 0. Consequently, the phase glass is unique in that it represents a concrete example of a metallic state that is mediated by disorder, even in 2D. We propose that the experimentally observed metallic phase which intervenes between the insulator and the superconductor in a wide range of thin films is in actuality a phase glass.
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Affiliation(s)
- Denis Dalidovich
- National High Field Magnetic Laboratory, Florida State University, Tallahassee, Florida, USA
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Himeda A, Kato T, Ogata M. Stripe states with spatially oscillating d-wave superconductivity in the two-dimensional t-t'-J model. PHYSICAL REVIEW LETTERS 2002; 88:117001. [PMID: 11909421 DOI: 10.1103/physrevlett.88.117001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2000] [Indexed: 05/23/2023]
Abstract
We study the interplay between stripes and d-wave superconductivity in the two-dimensional t-t'-J model using a variational Monte Carlo method. The next-nearest-neighbor hopping t'<0 stabilizes the stripe states around 1/8 hole doping rate. We find that stripes and spatially oscillating superconductivity coexist depending on parameters. The superconducting orders are enhanced at the hole stripe regions. Although the energy differences are relatively small, the stripe state in which the phases between adjacent superconducting stripes are the opposite (antiphase) is also stabilized. We consider the possibility that the antiphase coexistence may explain the weakness of the c-axis Josephson couplings in the La1.6-xNd0.4SrxCuO4.
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Affiliation(s)
- A Himeda
- Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
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Kawamura H, Li MS. Monte Carlo studies of the ordering of ceramic superconductors: Chiral-glass, orbital-glass, and nonlinear susceptibilities. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:619-636. [PMID: 9984298 DOI: 10.1103/physrevb.54.619] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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He Y, Muirhead CM, Vinen WF. Paramagnetic Meissner effect in high-temperature superconductors: Experiments and interpretation. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:12441-12453. [PMID: 9982878 DOI: 10.1103/physrevb.53.12441] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Chen D, Moreno JJ, Hernando A. Phi 0/2 vortices in a defect-containing Josephson-junction array. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:R9859-R9862. [PMID: 9980132 DOI: 10.1103/physrevb.52.r9859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Ishizaka S, Sone J, Ando T. dc Josephson current through a quantum dot coupled with superconducting leads. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:8358-8362. [PMID: 9979838 DOI: 10.1103/physrevb.52.8358] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Magnusson J, Björnander M, Pust L, Svedlindh P, Nordblad P, Lundström T. Time dependence of the magnetization of Bi2Sr2CaCu2O8 displaying the paramagnetic Meissner effect. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:7675-7681. [PMID: 9979712 DOI: 10.1103/physrevb.52.7675] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kuklov AB, Krakovsky A, Birman JL. Interlayer vortices and edge dislocations in high-temperature superconductors. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:623-628. [PMID: 9979642 DOI: 10.1103/physrevb.52.623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Magnusson J, Andersson J, Björnander M, Nordblad P, Svedlindh P. Time dependence of the paramagnetic Meissner effect: Comparison between model calculations and experiments. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:12776-12781. [PMID: 9978054 DOI: 10.1103/physrevb.51.12776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kuklov AB, Boyko VS, Malinsky J. Instability in the current-biased 0- pi Josephson junction. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:11965-11968. [PMID: 9977945 DOI: 10.1103/physrevb.51.11965] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kirtley JR, Tsuei CC, Sun JZ, Chi CC, Yu-Jahnes LS, Gupta A, Rupp M, Ketchen MB. Symmetry of the order parameter in the high-Tc superconductor YBa2Cu3O7- δ. Nature 1995. [DOI: 10.1038/373225a0] [Citation(s) in RCA: 309] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Chen D, Hernando A. Magnetization of symmetric 0- pi Josephson junctions. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:10107-10116. [PMID: 9975094 DOI: 10.1103/physrevb.50.10107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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49
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Tsuei CC, Kirtley JR, Chi CC, Gupta A, Shaw T, Sun JZ, Ketchen MB. Pairing symmetry and flux quantization in a tricrystal superconducting ring of YBa2Cu3O7- delta. PHYSICAL REVIEW LETTERS 1994; 73:593-596. [PMID: 10057486 DOI: 10.1103/physrevlett.73.593] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Rodrigues P, Schaf J, Pureur P. Field and oxygen dependence of the magnetic irreversibility line in YBa2Cu3O7- delta. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:15292-15298. [PMID: 10010641 DOI: 10.1103/physrevb.49.15292] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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