Effect of impurity scattering on superconductivity in K$_2$Cr$_3$As$_3$

TL;DR

This study investigates how nonmagnetic impurity scattering affects the superconducting transition temperature in K$_2$Cr$_3$As$_3$, providing evidence for non-$s$-wave pairing symmetry through resistivity and impurity analysis.

Contribution

It demonstrates the impact of impurity scattering on $T_c$ in K$_2$Cr$_3$As$_3$, supporting non-$s$-wave superconductivity via experimental resistivity data and pair-breaking theory.

Findings

Impurity scattering reduces $T_c$ significantly.

High-purity crystals have longer mean free paths.

Results align with Abrikosov-Gor'kov theory for non-$s$-wave pairing.

Abstract

Impurity scattering in a superconductor may serve as an important probe for the nature of superconducting pairing state. Here we report the impurity effect on superconducting transition temperature $T_\mathrm{c}$ in the newly discovered Cr-based superconductor K$_2$Cr$_3$As$_3$. The resistivity measurements show that the crystals prepared using high-purity Cr metal ($\geq$99.99\%) have an electron mean free path much larger than the superconducting coherence length. For the crystals prepared using impure Cr that contains various \emph{nonmagnetic} impurities, however, the $T_\mathrm{c}$ decreases significantly, in accordance with the generalized Abrikosov-Gor'kov pair-breaking theory. This finding supports a non-$s$-wave superconductivity in K$_2$Cr$_3$As$_3$.