Enhanced superconducting properties in FeCr$_x$Se

TL;DR

This study demonstrates that substituting excess Chromium at the Iron site in FeSe enhances its superconducting transition temperature and volume fraction, highlighting the influence of chemical pressure on superconductivity.

Contribution

It reveals that Cr substitution in FeSe in excess improves superconducting properties, a novel approach to tuning superconductivity via chemical pressure.

Findings

$T_c$ increases to 11.2 K with 2% Cr substitution

Superconducting volume fraction improves with Cr doping

Chemical pressure influences superconducting behavior

Abstract

We report an enhancement of superconducting transition temperature ($T_{\rm c}$) when Chromium (Cr) is substituted in excess at the Iron (Fe) site (FeCr$_x$Se, $x=$0.01, 0.02 and 0.03). There is a corresponding increase in the superconducting volume fraction with $T_{\rm c}$ attaining a value of 11.2 K on 2 $%$ Cr substitution when compared to a $T_{\rm c}$ of 8.5 K for the conventional tetragonal Fe-excess sample Fe$_{1+x}$Se. The results point to the role of chemical pressure (introduced via ionic size variation at the Fe site upon Cr substitution in excess) on superconducting properties.