Anomalous diamagnetic response in multi-band superconductors with time-reversal broken symmetry

TL;DR

This paper uses Ginzburg-Landau theory to identify conditions for time-reversal symmetry breaking in multi-band superconductors and predicts magnetic flux-induced current jumps as experimental signatures.

Contribution

It analytically establishes conditions for BTRS in multi-band superconductors and explores magnetic flux effects in a three-band model, proposing a new experimental detection method.

Findings

Magnetic flux can induce current jumps related to BTRS transitions.

Conditions for BTRS ground states are analytically derived.

Magnetic response can distinguish BTRS states experimentally.

Abstract

Within a Ginzburg-Landau formalism we establish analytically the necessary and sufficient conditions to realize a doubly degenerate superconducting ground state with broken time-reversal symmetry (BTRS) in a multi-band superconductor. Using these results we analyze the ground state of a three-band superconductor in the cylindrical geometry in an external magnetic field. We show that depending on the interband coupling constants, a magnetic flux can induce current density jumps in such superconducting geometries that are related to adiabatic or non-adiabatic transitions from BTRS to time-reversal symmetric states and vice versa. This unusual current induced magnetic flux response can in principle be used experimentally to detect superconducting BTRS ground states as well as corresponding metastable excited states.