Tomasch Oscillations as Above-Gap Signature of Topological Superconductivity

Identifying topological superconductors remains a significant challenge in current experiments, which usually involve searching for topologically protected in-gap modes. Although some experiments reported the observation of such in-gap modes, they are contested due to other possible mechanisms (e.g., disorder) that could lead to similar signatures. In this work, we theoretically propose a novel distinction between two-dimensional conventional s-wave and topological p-wave superconductors by above-gap transport signatures. Our method utilizes the emergence of Tomasch oscillations of quasiparticles in a junction consisting of a superconductor sandwiched between two metallic leads. We demonstrate that the behaviour of the oscillations in conductance as a function of the interface barriers provides a distinctive signature for s-wave and p-wave superconductors; they become weaker as the barrier strength increases in s-wave superconductors, while they become more pronounced in p-wave superconductors, which we prove to be a direct manifestation of the pairing symmetries. Our method, therefore, can serve as a complimentary probe for identifying some classes of topological superconductors through the above-gap transport.