Enhanced superconductivity in hole-doped Nb$_{2}$PdS$_{5}$

TL;DR

This study demonstrates that Ru doping in Nb$_{2}$PdS$_{5}$ enhances superconductivity and the upper critical field, indicating robust multi-band superconductivity influenced by spin-orbit coupling.

Contribution

It provides new insights into how Ru doping enhances superconductivity and critical fields in Nb$_{2}$PdS$_{5}$, highlighting the role of spin-orbit coupling.

Findings

Superconductivity is enhanced with Ru doping.

Charge transport remains hole-dominated with multi-band characteristics.

The upper critical field exceeds the Pauli limit by about four times.

Abstract

We synthesized a series of Nb$_{2}$Pd$_{1-x}$Ru$_{x}$S$_{5}$ polycrystalline samples by a solid-state reaction method and systematically investigated the Ru-doping effect on superconductivity by transport and magnetic measurements. It is found that superconductivity is enhanced with Ru doping and is quite robust upon disorder. Hall coefficient measurements indicate that the charge transport is dominated by hole-type charge carriers similar to the case of Ir doping, suggesting multi-band superconductivity. Upon Ru or Ir doping, \emph H$_{c2}$/$\emph T_c$ exhibits a significant enhancement, exceeding the Pauli paramagnetic limit value by a factor of approximately 4. A comparison of $T_c$ and the upper critical field ($H_{c2}$) amongst the different doping elements on Pd site, reveals a significant role of spin--orbit coupling.