The effect of Ni doping on the electronic structure and superconductivity in the noncentrosymmetric ThCoC2

TL;DR

This study investigates how Ni doping affects the electronic structure and superconducting properties of ThCoC2, revealing an increase in density of states and electron-phonon coupling that correlates with enhanced superconductivity.

Contribution

The paper provides a detailed theoretical analysis of Ni doping effects on ThCoC2's electronic structure and electron-phonon interactions, supporting the electron-phonon coupling mechanism for superconductivity.

Findings

Ni doping increases the density of states at the Fermi level.

Electron-phonon coupling constant $mbda$ increases with Ni doping.

Enhanced $mbda$ correlates with higher $T_c$ in experiments.

Abstract

ThCoC$_2$ is a non-BCS, noncentrosymmetric superconductor with $T_c \simeq 2.5$~K, in which pairing mechanism was suggested to be either spin fluctuations or the electron-phonon coupling. Earlier experimental work revealed that $T_c$ can be greatly enhanced upon Ni doping in ThCo$_{1-x}$Ni$_x$C$_2$, up to 12~K for $x = 0.4$. In this work, using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA), the evolution of the electronic structure upon Ni doping was studied and the increase of the density of states at the Fermi level was found. The electron-phonon coupling constant $\lambda$ was calculated using the rigid muffin tin approximation (RMTA) and the increase in $\lambda(x)$ was found. This indirectly confirms the electron-phonon coupling scenario as the trend in $\lambda(x)$ is in qualitative agreement with the experiment when the electron-phonon pairing is assumed.