Discovery of Superconductivity in Non-centrosymmetric Semimetal LaRhGe₃

LaRhGe3 crystalizes in the non-centrosymmetric space group I4mm with a strong asymmetric spin-orbit coupling (ASOC) due to containing Rh[1], which makes it a promising platform to search for spin-triplet superconductivity with time-reversal symmetry breaking (TRSB) [2]. We have grown single crystals of LaRhGe₃ using a self-flux method for the first time. I present our discovery of Type-I superconductivity in LaRhGe₃ with evidence from heat capacity and µSR experiments, with a critical temperature T_c of 0.385 K and critical field H_c of 2.1 mT [3]. Despite the strong ASOC in LaRhGe₃, we do not detect any evidence for TRSB across T_c in LaRhGe₃ in our zero-field µSR experiment. Our results are consistent with LaRhGe₃ being a weak-coupling s-wave superconductor with a dominant singlet pairing. We also characterize the normal state of LaRhGe₃ with temperature and field dependent electrical transport. We find a non-saturating magnetroresistance at 2 K of 800% at 9 T, which is related to electron-hole compensation in LaRhGe₃. We comment on semimetallicity and topology from our band structure calculations on LaRhGe₃. Finally, we find that above the onset of superconductivity, LaRhGe₃ exhibits an unusual temperature dependence in its resistivity, ρ ~ T ³, suggestive of possible non-Fermi liquid behavior. To elucidate this we investigate the Raman spectra of LaRhGe₃ at low temperature.

[1] T. Kawai et al., JPSJ 77, 064717 (2008).

[2] M. Smidman et al., Rep. Prog. Phys. 80, 036501 (2017).

[3] M. Oudah, et al., in preparation.