Weak anisotropy of the superconducting upper critical field in Fe1.11Te0.6Se0.4 single crystals

TL;DR

This study measures the upper critical magnetic field in Fe1.11Te0.6Se0.4 single crystals, revealing high isotropic critical fields and unusual temperature dependence, suggesting three-dimensional Fermi surface effects.

Contribution

It provides the first detailed measurement of Hc2 in Fe1.11Te0.6Se0.4, showing isotropic superconductivity linked to its 3D Fermi surface topology.

Findings

High zero-temperature Hc2 approx 47T

Hc2 becomes isotropic at T=0

Superconductivity linked to 3D Fermi surface topology

Abstract

We have determined the resistive upper critical field Hc2 for single crystals of the superconductor Fe1.11Te0.6Se0.4 using pulsed magnetic fields of up to 60T. A rather high zero-temperature upper critical field of mu0Hc2(0) approx 47T is obtained, in spite of the relatively low superconducting transition temperature (Tc approx 14K). Moreover, Hc2 follows an unusual temperature dependence, becoming almost independent of the magnetic field orientation as the temperature T=0. We suggest that the isotropic superconductivity in Fe1.11Te0.6Se0.4 is a consequence of its three-dimensional Fermi-surface topology. An analogous result was obtained for (Ba,K)Fe2As2, indicating that all layered iron-based superconductors exhibit generic behavior that is significantly different from that of the high-Tc cuprates.