Anharmonicity of flux lattices and thermal fluctuations in layered superconductors

TL;DR

This paper investigates the elastic properties and thermal fluctuations of flux lattices in layered superconductors with Josephson coupling, revealing non-traditional elastic behavior and phase transitions influenced by temperature and magnetic field strength.

Contribution

It introduces a new approach to defining effective elastic constants in layered superconductors accounting for logarithmic energy terms.

Findings

Elastic constants are not strictly defined due to ln(flux displacement) terms.

Tilt modulus exhibits ln(T) dependence, affecting displacement behavior.

Phase transitions include layer decoupling and melting depending on field strength.

Abstract

We study elasticity of a perpendicular flux lattice in a layered superconductor with Josephson coupling between layers. We find that the energy contains ln(flux displacement) terms, so that elastic constants cannot be strictly defined. Instead we define effective elastic constants by a thermal average. The tilt modulus has terms with ln(T) which for weak fields, i.e. Josephson length smaller than the flux line spacing, lead to displacement square average proportional to T/ln(T). The expansion parameter indicates that the dominant low temperature phase transition is either layer decoupling at high fields or melting at low fields.