Vortex liquid crystals in anisotropic type II superconductors

TL;DR

This paper explores the phase transitions of vortex matter in anisotropic type II superconductors, proposing a two-step melting process involving vortex smectic and nematic phases driven by fluctuations.

Contribution

It introduces the concept of a two-step vortex lattice melting in anisotropic superconductors, highlighting the role of fluctuations in stabilizing intermediate liquid crystalline phases.

Findings

Fluctuations favor an instability to a vortex smectic-A phase.

A two-step melting process from lattice to smectic to nematic is proposed.

Anisotropic superfluid stiffness influences vortex phase behavior.

Abstract

In a type II superconductor in a moderate magnetic field, the superconductor to normal state transition may be described as a phase transition in which the vortex lattice melts into a liquid. In a biaxial superconductor, or even a uniaxial superconductor with magnetic field oriented perpendicular to the symmetry axis, the vortices acquire elongated cross sections and interactions. Systems of anisotropic, interacting constituents generally exhibit liquid crystalline phases. We examine the possibility of a two step melting in homogeneous type II superconductors with anisotropic superfluid stiffness from a vortex lattice into first a vortex smectic and then a vortex nematic at high temperature and magnetic field. We find that fluctuations of the ordered phase favor an instability to an intermediate smectic-A in the absence of intrinsic pinning.