The Nature of the Superconducting phase Transitions in Strongly type-II Superconductors in the Pauli Paramagnetic limit

TL;DR

This paper analyzes the nature of superconducting phase transitions in strongly type-II superconductors under the Pauli paramagnetic limit using a Gorkov-Ginzburg-Landau framework, revealing a dimensionality-dependent changeover from continuous to discontinuous transitions.

Contribution

It provides analytical expressions for free energy coefficients without gradient expansion and shows the transition changeover depends solely on electronic band dimensionality.

Findings

Transition changeover depends on electronic band dimensionality.

Analytical expressions derived without gradient expansion.

Changeover occurs in quasi-2D regimes below a critical crossover parameter.

Abstract

Superconducting phase transitions in strongly type-II superconductors in the Pauli paramagnetic limit are considered within the framework of the Gorkov-Ginzburg-Landau approach in the lowest Landau level approximation for both s and d-wave electron pairing. Simple analytical expressions for the quadratic and quartic coefficients in the order parameter expansion of the superconducting free energy are derived without relying on gradient or wavenumber expansions. The existence of a changeover from continuos to discontinuos superconducting phase transitions predicted to occur in the clean limit is shown to depend only on the dimensionality of the underlying electronic band structure. Such a changeover can take place in the quasi 2D regime below a critical value of a 3D-2D crossover parameter.