SR study on the noncentrosymmetric superconductor NbGe

Jiao, J. C.*; Chen, K. W.*; Hillier, A. D.*; Ito, Takashi   ; Higemoto, Wataru  ; Li, Z.*; Lv, B.*; Xu, Z.-A.*; Shu, L.*

We report on a muon spin relaxation (SR) study on the polycrystalline noncentrosymmetric superconductor NbGe with superconducting transition temperature = 2.0-2.1 K. The zero-field SR experiment indicates the absence of a spontaneous magnetic field in the superconducting state, showing the preservation of time-reversal symmetry in the superconducting state. The transverse-field SR experiment is performed to map the phase diagram of NbGe, from which clear evidence of both type-I and type-II superconductivities is obtained. More importantly, we clearly delineate the region in the phase diagram where type-I and type-II superconductivities coexist.