| 1. |
- Bezugly, Eugene, et al.
(författare)
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Subgap current in superconducting tunnel junctions with diffusive electrodes
- 2006
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- We calculate subgap current in planar superconducting tunnel junctions with thin-film diffusive leads. It is found that the subharmonic gap structure of the tunnel current scales with an effective tunneling transparency which may exceed the junction transparency by up to two orders of magnitude depending on the junction geometry, and the ratio between the coherence length and the elastic scattering length. These results provide an alternative explanation of anomalously high values of the subgap current in tunnelling experiments often ascribed to imperfectness of the insulating layer. We also discuss the effect of finite lifetime of quasiparticles as the possible origin of additional enhancement of multiparticle tunnel currents.
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| 2. |
- Bezuglyi, Eugene, et al.
(författare)
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Multiparticle tunnelling in diffusive superconducting junctions
- 2007
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 20:6, s. 529-541
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Tidskriftsartikel (refereegranskat)abstract
- We formulate a theoretical framework to describe multiparticle current transport in planar superconducting tunnel junctions with diffusive electrodes. The approach is based on the direct solving of quasiclassical Keldysh-Green function equations for nonequilibrium superconductors, and consists of a combination of circuit theory analysis and improved perturbation expansion. The theory predicts a much greater scaling parameter for the subharmonic gap structure of the tunnel current in diffusive junctions compared to the one in ballistic junctions and mesoscopic constrictions with the same barrier transparency. © IOP Publishing Ltd.
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| 3. |
- Bezuglyi, Eugene, et al.
(författare)
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Nonequilibrium and relaxation effects in tunnel superconducting junctions
- 2017
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 30:2
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Tidskriftsartikel (refereegranskat)abstract
- The specific property of a planar tunnel junction with thin-film diffusive plates and long enough leads is an essential enhancement of its transmission coefficient compared to the bare transparency of the tunnel barrier [1, 2]. In voltage-biased junctions, this creates favorable conditions for strong nonequilibrium of quasiparticles in the junction plates and leads, produced by multiparticle tunneling. We study theoretically the interplay between the nonequilibrium and relaxation processes in such junctions and found that nonequilibrium in the leads noticeably modifies the currentvoltage characteristic at eV > 2D, especially the excess current, whereas strong diffusive relaxation restores the result of the classical tunnel model. At eV > 2D, the diffusive relaxation decreases the peaks of the multiparticle currents. The inelastic relaxation in the junction plates essentially suppresses the n-particle currents (n > 2) by the factor n for odd and n 2 for even n. The results may be important for the problem of decoherence in Josephsonjunction based superconducting qubits.
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| 4. |
- Bezuglyi, Eugene, et al.
(författare)
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Nonequilibrium effects in tunnel Josephson junctions
- 2005
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- We study nonequilibrium effects in current transport through voltage biased tunnel junction with long diffusive superconducting leads at low applied voltage eV 2Δ, and finite temperatures. Due to a small value of the Josephson frequency, the quasiparticle spectrum adiabatically follows the time evolution of the superconducting phase difference, which results in the formation of oscillating bound states in the vicinity of the tunnel junction (Andreev band). The quasiparticles trapped by the Andreev band generate higher even harmonics of the. Josephson ac current, and also, in the presence of inelastic scattering, a nonequilibrium dc current, which may considerably exceed the dc quasiparticle current given by the tunnel model. The distribution of traveling quasiparticles also deviates from the equilibrium due to the spectrum oscillations, which results in an additional contribution to the dc current, proportional to V.
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| 5. |
- Gordeeva, A. V., et al.
(författare)
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Record electron self-cooling in cold-electron bolometers with a hybrid superconductor-ferromagnetic nanoabsorber and traps
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. Radioastronomy instruments for CMB investigation require low working temperatures around 100 mK to get the necessary sensitivity. On-chip electron cooling of receivers is a pathway for future space missions due to problems of dilution fridges at low gravity. Here, we demonstrate experimentally that in a Cold-Electron Bolometer (CEB) a theoretical limit of electron cooling down to 65 mK from phonon temperature of 300 mK can be reached. It is possible due to effective withdrawing of hot electrons from the tunnel barrier by double stock, special traps and suppression of Andreev Joule heating in hybrid Al/Fe normal nanoabsorber.
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| 6. |
- Vasenko, Andrey, 1974
(författare)
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Dissipative Processes in Superconducting Diffusive Tunnel Junctions
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A central subject of this thesis is the dissipative current transport in superconducting tunnel junctions with diffusive electrodes. Tunnel current transport in superconducting junctions is a classical topic of interest and research. Our investigation is focused on the most interesting from the physical viewpoint region of small applied voltages, where the charge is carried by multiparticle tunneling processes, and strong nonequilibrium quasiparticle distribution is established. Such a study required development of a theoretical formalism going beyond the tunnel model approximation and based on a general nonequilibrium Keldysh-Green function technique for diffusive superconductors. Recently the problem attracted new attention motivated by development of transmissive tunnel structures, in particular, with high temperature superconductors, and by the problem of decoherence in Josephson junction based superconducting qubits.The first part of the thesis (paper 1) is devoted to nonequilibrium effects at low applied voltage and finite temperatures. Due to a small value of the Josephson frequency, the quasiparticle spectrum adiabatically follows the time evolution of the superconducting phase difference, which results in the formation of oscillating bound states in the vicinity of the tunnel junction (Andreev band). The quasiparticles trapped by the Andreev band generate higher even harmonics of the Josephson ac current, and also, in the presence of inelastic scattering, a nonequilibrium dc current, which may considerably exceed the dc quasiparticle current given by the tunnel model. The distribution of travelling quasiparticles also deviates from the equilibrium due to the spectrum oscillations, which results in an additional contribution to the dc current, proportional to the square root of applied voltage.In the second part of the thesis (papers 2 and 3), we examine the subharmonic gap structure (SGS) in the tunnel current focusing on the effect of diffusive electrodes and junction geometry. The main result is that the SGS features scale with an effective tunneling transparency which may exceed the junction transparency by up to two orders of magnitude depending on the junction geometry, and the ratio between the coherence length and the elastic scattering length. Our result provides an alternative explanation of anomalously high values of the subgap current in tunnelling experiments often ascribed to imperfectness of the insulating layer.
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| 7. |
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