Thermal fluctuations and disorder effect on the square-rhombic structural phase transition of the vortex lattice in tetragonal superconductors

Abstract

Influence of the thermal fluctuations and weak disorder on the square--rhombic transition of the vortex lattice in tetragonal superconductors is investigated using the Ginzburg Landau approach which is valid near the H-c2(T) line. In both cases the phase transition line in the T-H plane shifts in a way that makes the region occupied by the more symmetric square phase larger.