The phase transition phenomena in anisotropic superconductors: effect of the orthorhombic crystal field and the potential impurity scattering

TL;DR

This paper investigates how orthorhombic crystal fields and impurity scattering influence phase transitions in anisotropic superconductors, revealing distinct thermodynamic signatures that can identify specific pairing states in cuprate materials.

Contribution

It provides a theoretical analysis of impurity effects on superconducting states with tetragonal symmetry, highlighting how nonmagnetic impurities stabilize certain states and affect specific heat jumps.

Findings

Impurities stabilize states in the identity irreducible representation.

Distinct specific heat jump behaviors for different order parameters.

Predicted signals differentiate d_{x^2-y^2} and d_{xy} states in cuprates.

Abstract

A combined effect of the orthorhombic crystal field and potential impurity scattering on several superconducting states of a tetragonal symmetry is studied within a weak-coupling mean field approach. It is shown that the nonmagnetic impurities stabilize the states belonging to the identity irreducible representation. The electronic specific heat jump at the phase transition is analyzed. Its dependence on the potential scattering rate for large impurity concentration is shown to be remarkably different for the states with a nonzero value of the Fermi surface averaged order parameter than for those with a vanishing one. In particular, very distinct signals from d_{x^2-y^2} state in YBCO and d_{xy} state in BSCCO compound are predicted. This effect may be used as a test for the presence of these states in the above cuprates.