Browsing by Author "Khaymovich, I. M."

Now showing 1 - 8 of 8
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    Charge-vortex interplay in a superconducting Coulomb-blockaded island
    (2015-07-06) Khaymovich, I. M.; Maisi, V. F.; Pekola, J. P.; Mel'nikov, A.S.; Department of Applied Physics; Quantum Phenomena and Devices
    We show that charge transfer through a small superconducting (S) island of a single-electron transistor is strongly affected by vorticity. This interplay of charge and rotational degrees of freedom in a mesoscopic superconductor occurs through the effect of vorticity on the quantum mechanical spectrum of electron-hole excitations. The subgap quasiparticle levels in vortices can host an extra electron, thus suppressing the so-called parity effect in the S island. We propose to measure the collective dynamics of vorticity and electric charge via the charge pumping effect caused by alternating vortex entry and exit controlled by a periodic magnetic field.
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    Distribution of current fluctuations in a bistable conductor
    (2016-12-27) Singh, S.; Peltonen, Joonas; Khaymovich, I. M.; Koski, J. V.; Flindt, C.; Pekola, J. P.; Department of Applied Physics; Quantum Phenomena and Devices; Quantum Transport
    We measure the full distribution of current fluctuations in a single-electron transistor with a controllable bistability. The conductance switches randomly between two levels due to the tunneling of single electrons in a separate single-electron box. The electrical fluctuations are detected over a wide range of time scales and excellent agreement with theoretical predictions is found. For long integration times, the distribution of the time-averaged current obeys the large-deviation principle. We formulate and verify a fluctuation relation for the bistable region of the current distribution.
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    Electronic structure of a mesoscopic superconducting disk: Quasiparticle tunneling between the giant vortex core and the disk edge
    (American Physical Society, 2019-04-15) Pekola, J. P.; Samokhvalov, A.; Shereshevskii, I. A.; Vdovicheva, N. K.; Taupin, M.; Khaymovich, I. M.; Mel'nikov, A. S.; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Quantum Phenomena and Devices; Lobachevsky State University of Nizhni Novgorod; Russian Academy of Sciences; Vienna University of Technology
    The electronic structure of the giant vortex states in a mesoscopic superconducting disk is studied in a dirty limit using the Usadel approach. The local density of states profiles are shown to be strongly affected by the effect of quasiparticle (QP) tunneling between the states localized in the vortex core and the ones bound to the sample edge. Decreasing temperature leads to a crossover between the edge-dominated and core-dominated regimes in the magnetic field dependence of the tunneling conductance. This crossover is discussed in the context of the efficiency of quasiparticle cooling by the magnetic-field-induced QP traps in various mesoscopic superconducting devices.
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    Nonlocality and dynamic response of Majorana states in fermionic superfluids
    (2017-12-08) Khaymovich, I. M.; Pekola, J. P.; Melnikov, A. S.; Department of Applied Physics; Quantum Phenomena and Devices; Lobachevsky State University of Nizhni Novgorod; Max Planck Institute for the Physics of Complex Systems
    We suggest a microscopic model describing the nonlocal ac response of a pair of Majorana states in fermionic superfluids beyond the tunneling approximation. The time-dependent perturbations of quasiparticle transport are shown to excite finite period beating of the wavefunction between the distant Majorana states. We propose an experimental test to measure the characteristic time scales of quasiparticle transport through the pair of Majorana states defining, thus, quantitative characteristics of nonlocality known to be a generic feature of Majorana particles.
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    A random matrix model with localization and ergodic transitions
    (2015) Kravtsov, V.E.; Khaymovich, I. M.; Cuevas, E.; Amini, M.; Department of Applied Physics; Quantum Phenomena and Devices
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    Single Quantum Level Electron Turnstile
    (2016-04-20) Van Zanten, D. M T; Basko, D. M.; Khaymovich, I. M.; Pekola, J. P.; Courtois, H.; Winkelmann, C. B.; Université Grenoble Alpes; CNRS; Department of Applied Physics
    We report on the realization of a single-electron source, where current is transported through a single-level quantum dot (Q) tunnel coupled to two superconducting leads (S). When driven with an ac gate voltage, the experiment demonstrates electron turnstile operation. Compared to the more conventional superconductor-normal-metal-superconductor turnstile, our superconductor-quantum-dot-superconductor device presents a number of novel properties, including higher immunity to the unavoidable presence of nonequilibrium quasiparticles in superconducting leads. Moreover, we demonstrate its ability to deliver electrons with a very narrow energy distribution.
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    Thermodynamics in single-electron circuits and superconducting qubits
    (Annual Reviews Inc., 2019-03-10) Pekola, J. P.; Khaymovich, I. M.; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Quantum Phenomena and Devices
    Classical and quantum electronic circuits provide ideal platforms to investigate stochastic thermodynamics, and they have served as a stepping stone to realize Maxwell's Demons with highly controllable protocols. In this article, we first review the central thermal phenomena in quantum nanostructures. Thermometry and basic refrigeration methods are described as enabling tools for thermodynamics experiments. Next, we discuss the role of information in thermodynamics that leads to the concept of Maxwell's Demon. Various Maxwell's Demons realized in single-electron circuits over the past couple of years are described. Currently, true quantum thermodynamics in superconducting circuits is a focus of attention, and we end the review by discussing the ideas and first experiments in this exciting area of research.
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    Tunable quasiparticle trapping in Meissner and vortex states of mesoscopic superconductors
    (2016-03) Taupin, M.; Khaymovich, I. M.; Meschke, M.; Mel'nikov, A. S.; Pekola, J. P.; Department of Applied Physics; Quantum Phenomena and Devices; Lobachevsky State University of Nizhni Novgorod
    Nowadays, superconductors serve in numerous applications, from high-field magnets to ultrasensitive detectors of radiation. Mesoscopic superconducting devices, referring to those with nanoscale dimensions, are in a special position as they are easily driven out of equilibrium under typical operating conditions. The out-of-equilibrium superconductors are characterized by non-equilibrium quasiparticles. These extra excitations can compromise the performance of mesoscopic devices by introducing, for example, leakage currents or decreased coherence time in quantum devices. By applying an external magnetic field, one can conveniently suppress or redistribute the population of excess quasiparticles. In this article, we present an experimental demonstration and a theoretical analysis of such effective control of quasiparticles, resulting in electron cooling both in the Meissner and vortex states of a mesoscopic superconductor. We introduce a theoretical model of quasiparticle dynamics, which is in quantitative agreement with the experimental data.