$\hat{I}¼$SR study on noncentrosymmetric superconductor NbGe${}_2$

Abstract

We report a muon spin relaxation ($\hat{I}¼$SR) study on polycrystalline noncentrosymmetric superconductor NbGe${}_2$~with the superconducting transition temperature $T_c=2.0\sim 2.1$~K. Zero-field $\hat{I}¼$SR~experiment indicates the absence of spontaneous magnetic field in the superconducting state, showing the preservation of time-reversal symmetry in the superconducting state. Transverse-field $\hat{I}¼$SR~experiment is performed to map the phase diagram of NbGe${}_2$, from which clear evidence of both type-I and type-II superconductivity is obtained. More importantly, we clearly delineate the region in the phase diagram where type-I and type-II superconductivity coexist.

Accepted by Physical. Rev. B