Observation of Resonant Andreev Plateau from Chiral Hinge Modes in FeTe_0.55Se_0.45

Finding unique signatures of chiral hinge modes emerging in topological superconductors has been an ongoing challenge for condensed matter physicists. Here we report the development of a new method to do this in FeTe_0.55Se_0.45 (FTS) via Point Contact Andreev tunnelling measurements. We observe an abnormal conductance plateau around zero-bias voltage, indicating resonant Andreev reflections associated with 1D higher-order topological superconducting (1D-HOTSC) chiral hinge modes. The Andreev conductance plateau signal can only be detected with devices properly fabricated such that the current leads touch only the hinge. This is confirmed by demonstrating the protection is removed by changing the ground to different regions of the sample. Moreover, the abnormal conductance plateau is remarkably robust and reproducible, remaining stable in high magnetic fields and displaying temperature dependence that strays from the normal Andreev reflection processes at metal/trivial-superconductor interfaces. Our observed signal can rule out almost all trivial explanations and provides strong evidence of 1D-HOTSC chiral modes along the hinges of topologically non-trivial FTS samples.