부산대학교 도서관

Second-order topological insulators are characterized by helical, non-spin-degenerate one-dimensional states running along opposite crystal hinges with no backscattering. Injecting superconducting pairs therefore entails splitting Cooper pairs into two families of helical Andreev states of opposite helicity, one at each hinge. Here we provide evidence for such separation via the measurement and analysis of the switching supercurrent statistics of a crystalline nanoring of bismuth. Using a phenomenological model of two helical Andreev hinge modes, we find that pairs relax at a rate comparable to individual quasiparticles, in contrast to the much faster pair relaxation of non-topological systems. This constitutes a unique telltale sign of the spatial separation of topological helical hinges.
Second-order topological insulators feature helical one-dimensional states located at crystal hinges. Running a supercurrent through such systems is now shown to lead to long-lived excited Andreev pairs due to their separation along hinges with opposite helicity.