Theoretical model for hysteresis and jumps in disordered 2D superconductors near SIT

by Mr. Shahar Kasirer

Bgu

at Condensed Matter Seminar

Mon, 21 Dec 2020, 11:30
Zoom

Abstract

***** Zoom link attached below ****
Many disordered superconductors have been shown to undergo a superconducting to insulating phase-transition (SIT) as a function of disorder or external magnetic field. The insulating phase has some unusual properties, among them is its I-V curve, which sometimes includes hysteresis and current jumps. Other systems, where a similar behavior was measured, are arrays of superconducting or normal islands, that are connected through tunneling junctions (Josephson junction and quantum dot arrays, respectively). Therefore, superconductors near SIT are usually modeled as disordered arrays. Transport properties are acquired by attributing resistance and capacitance to each junction, and treating tunneling as a perturbation to the states with a well defined number of charge carriers on each island. In those models, fast relaxation is usually assumed, meaning that the system restores equilibrium (electrostatic and thermal) quickly after each tunneling, and thus it is approximated as always being in equilibrium. Those models are successful in explaining some measurement results, including the phase transition itself, but fail to reproduce hysteresis and jumps. In this talk, I will present our investigation of the slow relaxation limit, where equilibrium is not restored between tunnelings. In it, we used a model for a single conducting island, that was suggested by Korotkov[1]. We analyzed its transport properties, and generalized it into a random array model. Disorder was realized by randomly assigning resistance and capacitance to tunneling junctions. Using Kinetic Monte-Carlo simulations, we calculated the voltage and temperature dependencies of the current, for different disorder realizations. Results show that our model can reproduce hysteresis and current jumps, for certain parameters, and are in qualitative agreement with experimental results. I will conclude the talk with suggestions for ways in which our model can be used for future research.

1. Korotkov, A. N. Single-electron transistor controlled with a RC circuit. Physical Review B 49, 16518–16522 (June 1994).


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Created on 16-12-2020 by Meidan, Dganit (dganit)
Updaded on 21-12-2020 by Meidan, Dganit (dganit)