Upper Critical Field of the 3 Kelvin Phase in Sr2RuO4

TL;DR

This paper investigates the upper critical field behavior of the 3 Kelvin superconducting phase in Sr2RuO4, revealing a sublinear temperature dependence explained by a Ginzburg-Landau model of filamentary spin-triplet superconductivity.

Contribution

It introduces a Ginzburg-Landau analysis of the filamentary 3 Kelvin phase, explaining its unique H_{c2}(T) behavior with a two-component order parameter.

Findings

H_{c2}(T) follows a sublinear power law with 0.5 ≤ γ < 1

The filamentary phase is modeled as a finite-width superconducting region

The two-component order parameter explains the observed critical field behavior

Abstract

The inhomogeneous 3 Kelvin phase is most likely a superconducting state nucleating at the interface between micrometer-sized Ru-metal inclusions and Sr2RuO4 above the bulk onset of superconductivity. This filamentary superconducting state yields a characteristic temperature dependence of the upper critical field which is sublinear, i.e., H_{c2} (T) \propto (T^* - T)^{\gamma} with 0.5 \leq \gamma < 1 (T^*: nucleation temperature). The Ginzburg-Landau theory is used to analyze the behavior of the nucleated spin-triplet phase in a field and the characteristic features of H_{c2} observed in the experiment are explained based on a two-component order parameter in the presence of a filament of enhanced superconductivity with a finite width.