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Plaszkó NL, Rakyta P, Cserti J, Kormányos A, Lambert CJ. Quantum Interference and Nonequilibrium Josephson Currents in Molecular Andreev Interferometers. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1033. [PMID: 32481631 PMCID: PMC7420291 DOI: 10.3390/nano10061033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/20/2020] [Accepted: 05/21/2020] [Indexed: 02/05/2023]
Abstract
We study the quantum interference (QI) effects in three-terminal Andreev interferometers based on polyaromatic hydrocarbons (PAHs) under non-equilibrium conditions. The Andreev interferometer consists of a PAH coupled to two superconducting and one normal conducting terminals. We calculate the current measured in the normal lead as well as the current between the superconducting terminals under non-equilibrium conditions. We show that both the QI arising in the PAH cores and the bias voltage applied to a normal contact have a fundamental effect on the charge distribution associated with the Andreev Bound States (ABSs). QI can lead to a peculiar dependence of the normal current on the superconducting phase difference that was not observed in earlier studies of mesoscopic Andreev interferometers. We explain our results by an induced asymmetry in the spatial distribution of the electron- and hole-like quasiparticles. The non-equilibrium charge occupation induced in the central PAH core can result in a π transition in the current-phase relation of the supercurrent for large enough applied bias voltage on the normal lead. The asymmetry in the spatial distribution of the electron- and hole-like quasiparticles might be used to split Cooper pairs and hence to produce entangled electrons in four terminal setups.
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Affiliation(s)
- Noel L. Plaszkó
- Department of Physics of Complex Systems, Eötvös Loránd University, Budapest 1095, Pázmány P. s. 1/A, Hungary; (N.L.P.); (P.R.); (J.C.)
| | - Peter Rakyta
- Department of Physics of Complex Systems, Eötvös Loránd University, Budapest 1095, Pázmány P. s. 1/A, Hungary; (N.L.P.); (P.R.); (J.C.)
| | - József Cserti
- Department of Physics of Complex Systems, Eötvös Loránd University, Budapest 1095, Pázmány P. s. 1/A, Hungary; (N.L.P.); (P.R.); (J.C.)
| | - Andor Kormányos
- Department of Physics of Complex Systems, Eötvös Loránd University, Budapest 1095, Pázmány P. s. 1/A, Hungary; (N.L.P.); (P.R.); (J.C.)
| | - Colin J. Lambert
- Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
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Stoutimore MJA, Rossolenko AN, Bolginov VV, Oboznov VA, Rusanov AY, Baranov DS, Pugach N, Frolov SM, Ryazanov VV, Van Harlingen DJ. Second-Harmonic Current-Phase Relation in Josephson Junctions with Ferromagnetic Barriers. PHYSICAL REVIEW LETTERS 2018; 121:177702. [PMID: 30411928 DOI: 10.1103/physrevlett.121.177702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Indexed: 06/08/2023]
Abstract
We report the observation of a current-phase relation dominated by the second Josephson harmonic in superconductor-ferromagnet-superconductor junctions. The exotic current-phase relation is realized in the vicinity of a temperature-controlled 0-to-π junction transition, at which the first Josephson harmonic vanishes. Direct current-phase relation measurements, as well as Josephson interferometry, nonvanishing supercurrent and half-integer Shapiro steps at the 0-π transition self-consistently point to an intrinsic second harmonic term, making it possible to rule out common alternative origins of half-periodic behavior. While surprising for diffusive multimode junctions, the large second harmonic is in agreement with theory predictions for thin ferromagnetic interlayers.
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Affiliation(s)
- M J A Stoutimore
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - A N Rossolenko
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
| | - V V Bolginov
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
- Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russia
- Russian National University of Science and Technology (NUST) MISiS, 4 Leninsky Prospect, Moscow 119049, Russia
| | - V A Oboznov
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
| | - A Y Rusanov
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
| | - D S Baranov
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
| | - N Pugach
- Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russia
- MIEM, National Research University Higher School of Economics, Moscow 101000, Russia
| | - S M Frolov
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - V V Ryazanov
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
- Russian National University of Science and Technology (NUST) MISiS, 4 Leninsky Prospect, Moscow 119049, Russia
- Faculty of Physics, National Research University Higher School of Economics, Moscow 101000, Russia
| | - D J Van Harlingen
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Golod T, Rydh A, Krasnov VM. Detection of the phase shift from a single Abrikosov vortex. PHYSICAL REVIEW LETTERS 2010; 104:227003. [PMID: 20867200 DOI: 10.1103/physrevlett.104.227003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Indexed: 05/22/2023]
Abstract
We probe a quantum mechanical phase rotation induced by a single Abrikosov vortex in a superconducting lead, using a Josephson junction, made at the edge of the lead, as a phase-sensitive detector. We observe that the vortex induces a Josephson phase shift equal to the polar angle of the vortex within the junction length. When the vortex is close to the junction it induces a π step in the Josephson phase difference, leading to a controllable and reversible switching of the junction into the 0-π state. This in turn results in an unusual Φ(0)/2 quantization of the flux in the junction. The vortex may hence act as a tunable "phase battery" for quantum electronics.
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Affiliation(s)
- T Golod
- Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden
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Braude V, Nazarov YV. Fully developed triplet proximity effect. PHYSICAL REVIEW LETTERS 2007; 98:077003. [PMID: 17359051 DOI: 10.1103/physrevlett.98.077003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Indexed: 05/14/2023]
Abstract
We present a model for the fully developed proximity effect in superconductor-ferromagnet heterostructures. Within the circuit-theory approximation, we evaluate the Green functions, the density of states, and the Josephson current which depend essentially on the magnetic configuration.
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Affiliation(s)
- V Braude
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
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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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Zutić I, Mazin I. Phase-sensitive tests of the pairing state symmetry in Sr(2)RuO(4). PHYSICAL REVIEW LETTERS 2005; 95:217004. [PMID: 16384173 DOI: 10.1103/physrevlett.95.217004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Indexed: 05/05/2023]
Abstract
Exotic superconducting properties of have provided strong support for an unconventional pairing symmetry. However, the extensive efforts over the past decade have not yet unambiguously resolved the controversy about the pairing symmetry in this material. While recent phase-sensitive experiments using flux modulation in Josephson junctions consisting of and a conventional superconductor have been interpreted as conclusive evidence for a chiral spin-triplet pairing, we propose here an alternative interpretation. We show that an overlooked chiral spin-singlet pairing is also compatible with the observed phase shifts in Josephson junctions and propose further experiments which would distinguish it from its spin-triplet counterpart.
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Affiliation(s)
- Igor Zutić
- Center for Computational Materials Science, Naval Research Laboratory, Washington, D.C. 20375, USA
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Bauer A, Bentner J, Aprili M, Della Rocca ML, Reinwald M, Wegscheider W, Strunk C. Spontaneous supercurrent induced by ferromagnetic pi junctions. PHYSICAL REVIEW LETTERS 2004; 92:217001. [PMID: 15245309 DOI: 10.1103/physrevlett.92.217001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Indexed: 05/24/2023]
Abstract
We present magnetization measurements of mesoscopic superconducting niobium loops containing a ferromagnetic (PdNi) pi junction. The loops are prepared on top of the active area of a micro-Hall sensor based on high mobility GaAs/AlGaAs heterostructures. We observe asymmetric switching of the loop between different magnetization states when reversing the sweep direction of the magnetic field. This provides evidence for a spontaneous current induced by the intrinsic phase shift of the pi junction. In addition, the presence of the spontaneous current near zero applied field is directly revealed by an increase of the magnetic moment with decreasing temperature, which results in half integer flux quantization in the loop at low temperatures.
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Affiliation(s)
- A Bauer
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany
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Giazotto F, Heikkilä TT, Taddei F, Fazio R, Pekola JP, Beltram F. Tailoring Josephson coupling through superconductivity-induced nonequilibrium. PHYSICAL REVIEW LETTERS 2004; 92:137001. [PMID: 15089638 DOI: 10.1103/physrevlett.92.137001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2003] [Indexed: 05/24/2023]
Abstract
The distinctive quasiparticle distribution existing under nonequilibrium in a superconductor-insulator-normal metal-insulator-superconductor mesoscopic line is proposed as a novel tool to control the supercurrent intensity in a long Josephson weak link. We present a description of this system in the framework of the diffusive-limit quasiclassical Green-function theory and take into account the effects of inelastic scattering with arbitrary strength. Supercurrent enhancement and suppression, including a marked transition to a pi junction, are striking features leading to a fully tunable structure.
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Affiliation(s)
- F Giazotto
- NEST-INFM & Scuola Normale Superiore, I-56126 Pisa, Italy.
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Lindström T, Charlebois SA, Tzalenchuk AY, Ivanov Z, Amin MHS, Zagoskin AM. Dynamical effects of an unconventional current-phase relation in YBCO dc SQUIDs. PHYSICAL REVIEW LETTERS 2003; 90:117002. [PMID: 12688956 DOI: 10.1103/physrevlett.90.117002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Indexed: 05/24/2023]
Abstract
The predominant d-wave pairing symmetry in high-temperature superconductors allows for a variety of current-phase relations in Josephson junctions, which is to a certain degree fabrication controlled. In this Letter, we report on direct experimental observations of the effects of a nonsinusoidal current-phase dependence in YBCO dc SQUIDs, which agree with the theoretical description of the system.
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Affiliation(s)
- T Lindström
- Department of Microelectronics and Nanoscience, Chalmers University of Technology and Göteborg University, Sweden.
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