First-order phase transition and tricritical point in multiband U(1) London superconductors

TL;DR

This paper investigates the nature of phase transitions in multiband U(1) London superconductors, revealing a tricritical point where the transition shifts from continuous to first-order due to vortex interactions.

Contribution

It demonstrates the existence of a tricritical point in multiband superconductors, showing the transition can become first-order under certain conditions, unlike single-component cases.

Findings

Identification of a tricritical point in multiband superconductors.

Evidence that vortex loop interactions induce a first-order transition.

Relevance of the mechanism to other multicomponent gauge theories.

Abstract

The order of the superconducting phase transition is a classical problem. Single-component type-2 superconductors exhibit a continuous "inverted-XY" phase transition, as was first demonstrated for U(1) lattice London superconductors by a celebrated duality mapping with subsequent backing by numerical simulations. Here we study this problem in multiband U(1) London superconductors and find evidence that by contrast the model has a tricritical point. The superconducting phase transition becomes first-order when the Josephson length is sufficiently large compared to the magnetic field penetration length. We present evidence that the fluctuation-induced dipolar interaction between vortex loops makes the phase transition discontinuous. We discuss that this mechanism is also relevant for the phase transitions in multicomponent gauge theories with higher broken symmetry.