Is the term "type-1.5 superconductivity" warranted by Ginzburg-Landau theory?

TL;DR

This paper demonstrates that within Ginzburg-Landau theory, two-band superconductors do not exhibit distinct type-1.5 behavior, as their order parameters vary on the same length scale, aligning with classic type-I and type-II classifications.

Contribution

It shows that Ginzburg-Landau theory predicts a single coherence length for two-band superconductors, challenging the concept of type-1.5 superconductivity.

Findings

Order parameters vary on the same length scale

Single GL parameter kappa determines superconductor type

Type-1.5 superconductivity is not supported within GL approximation

Abstract

It is shown that within the Ginzburg-Landau (GL) approximation the order parameters Delta1(r, T) and Delta2(r, T) in two-band superconductors vary on the same length scale, the difference in the zero-T coherence lengths xi0_i ~vF_i/Delta_i(0), i = 1, 2 notwithstanding. This amounts to a single physical GL parameter kappa and the classic GL dichotomy: kappa < 1/sqrt(2) for type-I and kappa > 1/sqrt(2) for type-II.