Vortex chains due to nonpairwise interactions and field-induced phase transitions between states with different broken symmetry in superconductors with competing order parameters

TL;DR

This paper investigates vortex chain formations and phase transitions in multicomponent superconductors with competing order parameters, revealing non-pairwise vortex interactions and symmetry-breaking transitions driven by external magnetic fields.

Contribution

It uncovers the role of multi-body interactions in vortex pattern formation and identifies a field-induced transition to a higher symmetry state with a coherent subdominant order parameter.

Findings

Vortex chains and pairs form due to non-pairwise interactions.

A phase transition from U(1) to U(1)×U(1) symmetry occurs under magnetic field.

Surface probes can detect subdominant condensates in vortex cores.

Abstract

We study superconductors with two order components and phase separation driven by intercomponent density-density interaction, focusing on the phase where only one condensate has non-zero ground-state density and a competing order parameter exists only in vortex cores. We demonstrate there, that multi-body intervortex interactions can be strongly non-pairwise, leading to some unusual vortex patterns in an external field, such as vortex pairs and vortex chains. We demonstrate that, in external magnetic field, such a system undergoes a field-driven phase transition from (broken) $U(1)$ to (broken) $U(1)\times U(1)$ symmetries, when the subdominant order parameter in the vortex cores acquires global coherence. Observation of these characteristic ordering patterns in surface probes may signal the presence of a subdominant condensate in the vortex core.