Physical properties of noncentrosymmetric superconductor Ru$_7$B$_3$

TL;DR

This study characterizes the superconducting properties of Ru$_7$B$_3$, a noncentrosymmetric superconductor, revealing its s-wave pairing, weak electron-phonon coupling, and potential spin triplet mixing due to broken inversion symmetry.

Contribution

It provides a comprehensive analysis of Ru$_7$B$_3$'s superconducting and normal state properties, including experimental and theoretical insights into its pairing symmetry and electronic structure.

Findings

Ru$_7$B$_3$ has a $T_C$ of 3.3 K and is an s-wave, single-band, type II superconductor.

Weak electron-phonon coupling characterizes its superconductivity.

Unusual resistivity 'kink' suggests possible spin triplet component due to noncentrosymmetry.

Abstract

Transition metal boride Ru$_7$B$_3$ was found to be a noncentrosymmetric superconductor with $T_{C}$ equal to 3.3 K. Superconducting and normal state properties of Ru$_7$B$_3$ were determined by a self-consistent analysis through resistivity($\rho_{xx}$ and $\rho_{xy}$), specific heat, lower critical field measurement and electronic band structure calculation. It is found that Ru$_7$B$_3$ belongs to an s-wave dominated single band superconductor with energy gap 0.5 meV and could be categorized into type II superconductor with weak electron-phonon coupling. Unusual 'kink' feature is clearly observed in field-broadening resistivity curves, suggesting the possible mixture of spin triplet induced by the lattice without inversion symmetry.