Microscopic derivation of two-component Ginzburg-Landau model and conditions of its applicability in two-band systems

TL;DR

This paper derives a two-component Ginzburg-Landau model for two-band superconductors from a microscopic perspective, clarifying its applicability and limitations, and highlighting its usefulness for studying vortex physics and magnetic responses.

Contribution

It provides a microscopic derivation of the two-component Ginzburg-Landau theory and identifies conditions for its validity in two-band superconductors.

Findings

Two-component GL theory is valid near $T_c$ and sometimes far from it.

The model effectively describes vortex physics and magnetic response.

Single GL parameter cannot characterize multiband magnetic behavior.

Abstract

We report a microscopic derivation of two-component Ginzburg-Landau (GL) field theory and the conditions of its validity in two-band superconductors. We also investigate the conditions when microscopically derived or phenomenological GL models fail and one should resort to a microscopic description. We show that besides being directly applicable at elevated temperatures, a version of a minimal two-component GL theory in certain cases also gives accurate description of certain aspects of a two-band system even substantially far from $T_c$. This shows that two-component GL model can be used for addressing a wide range of questions in multiband systems, in particular vortex physics and magnetic response. We also argue that single Ginzburg-Landau parameter cannot in general characterize magnetic response of multiband systems.