Helicity Modulus and Meissner Effect in a Fluctuating Type II Superconductor

TL;DR

This paper investigates the helicity modulus in a fluctuating type II superconductor to understand phase coherence and the Meissner effect, especially around the vortex lattice melting transition, highlighting the persistence of coherence under certain conditions.

Contribution

It introduces a calculation of the helicity modulus within the elastic medium approximation to analyze superconducting coherence and the Meissner effect in the mixed state of fluctuating type II superconductors.

Findings

Superconducting coherence persists parallel to the magnetic field at the vortex lattice melting transition.

A finite shear modulus in the vortex liquid indicates retained phase coherence.

The helicity modulus serves as a probe for superconducting phase coherence in the mixed state.

Abstract

The helicity modulus for a fluctuating type II superconductor is computed within the elastic medium approximation, as a probe of superconducting phase coherence and the Meissner effect in the mixed state. We argue that at the vortex line lattice melting transition, there remains superconducting coherence parallel to the applied magnetic field, provided the vortex line liquid retains a finite shear modulus at finite wavevector.