Large, Homogeneous, and Isotropic Critical Current Density in Oxygen-Annealed Fe1+yTe0.6Se0.4 Single Crystal

TL;DR

This study demonstrates that oxygen annealing effectively removes excess iron in Fe1+yTe0.6Se0.4 single crystals, inducing bulk superconductivity with high, nearly isotropic critical current densities and uniform current flow.

Contribution

It introduces a controllable oxygen annealing process to enhance superconductivity and current uniformity in Fe1+yTe0.6Se0.4 crystals, improving upon previous methods.

Findings

Oxygen annealing removes excess Fe and induces bulk superconductivity.

Critical current densities are large and nearly isotropic at 2 K.

Magneto-optical imaging shows isotropic current flow within the ab-plane.

Abstract

We reported a controllable way of removing excess Fe in Fe1+yTe0.6Se0.4 by annealing in a fixed amount of O2. Compared with the weak superconductivity induced by dilute acids, O2 annealing can successfully induce bulk superconductivity. Proper O2 annealing changes the temperature dependence of resistivity at low temperatures from semiconducting to metallic, which comes from the deintercalation of excess Fe. Critical current densities with field along the c-axis and ab-plane are found almost isotropic with large values of 3*10^5 A/cm2 and 2.5*10^5 A/cm2 at 2 K. Furthermore, magneto-optical images reveal isotropic current flow within the ab-plane.