Spectroscopic evidence of multi-gap superconductivity in non-centrosymmetric AuBe

AuBe is a chiral, non-centrosymmetric superconductor with transition temperature \(T_C\) \(\simeq\) 3.25 K. The broken inversion symmetry in its crystal structure makes AuBe a possible candidate to host a mixed singlet-triplet pairing symmetry in its superconducting order parameter (\(\Delta\)). This possibility was investigated by transport, thermodynamic, and muon-spin rotation/relaxation experiments in AuBe. However, this issue was not addressed using direct spectroscopic probes so far. In addition, certain ambiguities exist in the description of superconductivity in AuBe based on \(\mu\)SR experiments reported earlier. Here we report scanning tunneling spectroscopy (STS) on AuBe down to 300 mK. We found a signature of two superconducting gaps (with 2\(\Delta_1/k_{B}T_{C}\) = 4.37 and 2\(\Delta_2/k_{B}T_{C}\) = 2.46 respectively) and a clean BCS-like temperature dependence of both the gaps. We have also performed band structure calculations to identify the different bands that might give rise to the observed two-gap superconductivity in AuBe.