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

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($\ddot{I}{}_{xx}$ and $\ddot{I}{}_{xy}$), 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.

11 pages, 16 figures. submitted to Phys. Rev. B