Effects of Annealing under Tellurium Vapor for Fe$_{1.03}$Te$_{0.8}$Se$_{0.2}$ Single Crystals

TL;DR

This study demonstrates that annealing Fe$_{1.03}$Te$_{0.8}$Se$_{0.2}$ single crystals in tellurium vapor enhances their superconducting properties by removing excess iron, resulting in a transition at 13 K and full magnetic shielding.

Contribution

It introduces a tellurium vapor annealing method that effectively improves superconductivity in Fe-based single crystals by reducing excess iron content.

Findings

Superconductivity appears after annealing at 400°C for 250 hours.

Annealed crystals show a sharp transition at 13 K.

Full magnetic shielding effect is observed at low temperatures.

Abstract

In this study, the effects of annealing under tellurium vapor have been investigated for Fe$_{1.03}$Te$_{0.8}$Se$_{0.2}$ single crystals. The as-grown crystal is not superconducting. After annealing it at 400 $^\circ$C for 250 h in tellurium (Te) vapor, it shows metallic resistivity temperature dependence below 150 K and a sharp superconducting transition at 13 K. The sample also shows a full magnetic shielding effect at low temperatures. The improvement in superconductivity has been attributed to the removal of excess Fe, which is inevitably incorporated in the as-grown crystals, by the annealing.