Broken time-reversal symmetry detected by point-contact spectroscopy of superconducting Pd-doped CaAgP

Abstract

The appearance of broken time-reversal symmetry (TRS) in superconducting states is an intriguing issue in solid-state physics because of the incompatibility of the spontaneous magnetic field and the Meissner effect. We identify broken TRS in Pd-doped CaAgP (CaAg0.9Pd0.1P) by point-contact spectroscpy through the magnetic-field response of conductance spectra. CaAg0.9Pd0.1P is a nodal-line semi-metal with exotic electronic states such as drumhead surface states and surface superconductivity. Tunneling conductance spectra acquired at the side surfaces of CaAg0.9Pd0.1P under an applied magnetic field exhibit broad zero-bias peaks with small asymmetric structures. Surprisingly, the asymmetric structures are reversed exactly by flipping the field direction. On the basis of an analysis which stands on the formula of tunneling junctions for unconventional superconductors, these results are consistent with the pair potential of the superconductivity breaks with the TRS and is strongly coupled to an external magnetic field. We reveal the novel character of superconducting nodal-line semi-metals by developing the TRS sensitivity of point-contact spectroscopy. Our results serve as an exploration of broken TRS in superconducting states realized in topological materials.

Source-reported materials — not catalogue approval

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