Coexisting Topological Hinges and 1D Rashba States in Bi0.97Sb0.03 Revealed by the Josephson Effect.

Second-order topological insulating (SOTI) states in three-dimensional materials are helical one-dimensional hinge states. Inducing superconductivity in these states leads to gapless bound states, characterized by the 4π-periodic current-phase relation. Here, we provide evidence of the topologically protected hinge states in Dirac semimetal Bi0.97Sb0.03 nanoflakes by an unconventional interference pattern in a magnetic field and the 4π-periodic supercurrent carried by these states via the suppressed first and third Shapiro steps. Tight-binding simulations confirm the presence of multiple hinge modes, supporting our interpretation of Bi0.97Sb0.03 as a prototypical designable SOTI platform. The quantum confinement effect is identified by a quasi-one-dimensional bulk transport, and the confined Rashba states are responsible for the broadened hinge states.