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Low Temperature Physics

The discretization of a current and a magnetic field by a superconducting structure with an asymmetric quantum interferometer

С. И. Бондаренко, V. N. Fenchenko, V. P. Koverya, A. V. Krevsun

Published Aug 1, 2019• 1 citation
Publisher

Abstract

A mathematical model of the quantum processes in an asymmetric interferometer with an ultralow inductance L0 ≈ 10−13 H, shunted by a highly inductive superconducting circuit L1 >> L0 × 107 is constructed. The model is verified by comparing the calculated parameters of the model with the experimentally measured values.
DOI
10.1063/1.5116543

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The theory of self-induced resonances in asymmetric two-junction interferometer device is presented. In real devices, it is impossible to have an ideal interferometer free of imperfections. Thus, we extended previous theoretical approaches, introducing a model that contains several asymmetries: Josephson current ϵϵϵ, capacitances $\ensuremath{\chi}$, and dissipation $\ensuremath{\rho}$ presented in an equivalent circuit. Moreover, nonconventional symmetry of the order parameter in high temperature superconducting quantum interference devices forced us to include phase asymmetries. Therefore, the model has been extended to the case of $\ensuremath{\pi}$-shift interferometers, where a phase shift is present in one of the junctions.
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A digital computer was used to predict the operational characteristics for two models of a superconducting interferometer inductively coupled to an rf tank circuit. The interferometer is modeled by a weak link shunted by a resistor and a superconducting inductor. For a Josephson model, the current iJ and the phase difference across the weak link φ are related by iJ=ic sinφ. We have also examined the consequences of the relationship iJ∝∇φ (1+cosφ) which would result from a modified Aslamazov-Larkin two-phase model, where the supercurrent depends on both the phase difference φ and the phase gradient ∇φ in the weak link. We find that the (1+cosφ) model with the proper boundary condition can reproduce essentially all aspects of the experimental result for interferometers with proximity effect bridges. In particular, the two-phase model is adequate in describing the temperature dependence of the rf response, whereas the Josephson model does not.