Superconductivity at T_c ~ 14 K in Single Crystalline FeTe$_{0.61}$Se$_{0.39}$

TL;DR

This study reports the synthesis and detailed characterization of single crystalline FeTe$_{0.61}$Se$_{0.39}$ with a superconducting transition at approximately 14 K, highlighting the effects of annealing on its properties.

Contribution

The paper presents a new synthesis method for high-quality FeTe$_{0.61}$Se$_{0.39}$ crystals and analyzes how annealing influences their superconducting and chemical inhomogeneities.

Findings

Superconducting transition at ~14 K in synthesized crystals.

Critical current density exceeds 10^5 A/cm^2 below 5 K.

Weak fish-tail effect observed at lower temperatures.

Abstract

Single crystalline FeTe$_{0.61}$Se$_{0.39}$ with a sharp superconducting transition at $T_{\textrm{c}} \sim$ 14 K is synthesized via slow furnace cooling followed by low-temperature annealing. The effect of annealing on the chemical and superconducting inhomogeneities is carefully characterized. We also report resistivity, magnetization, and magneto-optical images of this crystal. Based on the Bean model, critical current density is estimated to exceed $1 \times 10^5$ A/cm$^2$ below 5 K under zero field. Weak fish-tail effect is identified at lower temperatures.