Possible superconductivity above 25 K in single crystalline Co-doped BaFe$_{2}$As$_{2}$

TL;DR

This study investigates the superconducting properties of Co-doped BaFe2As2 single crystals, revealing superconductivity above 25 K and suggesting potential for higher transition temperatures through doping optimization.

Contribution

The paper provides detailed measurements of superconducting properties in Co-doped BaFe2As2, including evidence of superconductivity above 25 K and insights into multiband behavior and vortex dynamics.

Findings

Superconductivity observed above 25 K in Co-doped BaFe2As2.

High critical current density exceeding 10^5 A/cm^2.

Anisotropic upper critical field with a ratio of about 3.5.

Abstract

We present superconducting properties of single crystalline Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ by measuring magnetization, resistivity, upper critical field, Hall coefficient, and magneto-optical images. The magnetization measurements reveal fish-tail hysteresis loop at high temperatures and relatively high critical current density above $J_{c}=10^{5}$ A/cm$^{2}$ at low temperatures. Upper critical field determined by resistive transition is anisotropic with anisotropic parameter $\sim$ 3.5. Hall effect measurements indicate that Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ is a multiband system and the mobility of electron is dominant. The magneto-optical imaging reveals prominent Bean-like penetration of vortices although there is a slight inhomogeneity in a sample. Moreover, we find a distinct superconductivity above 25 K, which leads us to speculate that higher transition temperature can be realized by fine tuning Co-doping level.