Fractional Flux Plateau in Magnetization Curve of Multicomponent Superconductor Loop

TL;DR

This paper demonstrates fractional flux plateaus in the magnetization curve of a multicomponent superconductor loop, providing evidence of time-reversal symmetry breaking and offering insights into phase kinks and solitons in such systems.

Contribution

It introduces the concept of fractional flux plateaus in TRSB multicomponent superconductors, linking them to domain walls and phase kinks, which is a novel experimental signature.

Findings

Fractional flux plateaus are observed in the magnetization curve.

Plateau heights are related to the flux quantum {} = hc/2e.

The phenomenon indicates broken time-reversal symmetry in superconductors.

Abstract

Time-reversal symmetry (TRS) may be broken in superconductors with three or more condensates interacting repulsively, yielding two degenerate states specified by chirality of gap functions. We consider a loop of such superconductor with two halves occupied by the two states with opposite chiralities. Fractional flux plateaus are found in magnetization curve associated with free-energy minima, where the two domain walls between the two halves accommodate different inter-component phase kinks leading to finite winding numbers in a part of the whole condensates around the loop. Fractional flux plateaus form pairs with their heights related to the flux quantum {\Phi}0 = hc/2e. This phenomenon is a clear evidence of time-reversal symmetry broken (TRSB) superconductivity, which in a general point of view provides a novel chance to explore relative phase difference, phase kink and soliton in ubiquitous multi-component superconductivity such as that in iron pnicitides.