Dc SQUID based on a three-band superconductor with broken time-reversal symmetry

TL;DR

This paper investigates a dc SQUID based on a three-band superconductor with broken time-reversal symmetry, revealing unique multi-hysteresis and multi-periodic behaviors due to the superconductor's complex ground state degeneracy.

Contribution

It introduces new features in dc SQUID characteristics arising from a BTRS three-band superconductor, highlighting complex flux dependencies and degeneracy effects.

Findings

Degeneracy of ground states at half-integer flux leads to multi-hysteresis loops.

Critical current dependencies exhibit multi-periodic, non-standard patterns.

Unique flux behavior differs from conventional SQUIDs and Fraunhofer patterns.

Abstract

The behavior of a dc SQUID, based on a dirty point contacts between a single-band and three-band superconductor with broken time-reversal symmetry is investigated. Using earlier obtained results for Josephson effects in such systems new features in characteristics of a dc SQUID are revealed. It is shown that in the case of a BTRS (broken time-reversal symmetry) three-band superconductor for the applied external magnetic flux, which is divisible by the half-integer flux, strong degeneracy of ground states of a dc SQUID is taken place. This can lead to the appearance of possible multi-hysteresis loops on a dependence of a total flux in the dc SQUID from the externally applied flux. The number of these loops depends on the position of ground states of a three-band superconductor. Also it is found that dependencies of a critical current on applied magnetic flux can have complicated multi-periodic forms, which are differ from strictly periodic characteristics for conventional dc SQUIDs and Fraunhofer patterns for Josephson contacts in the external magnetic field.