Isotropic superconducting state and high critical currents in Fe1+yTe1-xSx single crystals

TL;DR

This study reports the growth and analysis of Fe_{1+y}Te_{1-x}S_{x} single crystals, revealing an isotropic superconducting state with high critical currents and the lowest anisotropy among iron-based superconductors.

Contribution

It presents the first detailed investigation of superconducting anisotropy in Fe_{1+y}Te_{1-x}S_{x} crystals, highlighting their isotropic nature and high upper critical fields.

Findings

Smallest upper critical field anisotropy among iron-based superconductors

Isotropic superconducting state with gamma close to 1

Large upper critical fields maintained in the crystals

Abstract

We report single crystal growth and a study of superconducting properties in Fe_{1+y}Te_{1-x}S_{x}. We demonstrate the smallest upper critical field anisotropy, gamma=H_{c2}^{//c}/H_{c2}^{//a}, among all iron based superconductors, the value of gamma reaches 1.05 at T=0.65T_{C} for Fe_{1.09}Te_{0.89}S_{0.11}, while still maintaining large values of upper critical field.