Confined vs. extended Dirac surface states in topological crystalline insulator nanowires

Confining two-dimensional Dirac fermions on the surface of topological insulators has remained an outstanding conceptual challenge. In this work, we show that Dirac fermion confinement is achievable in topological crystalline insulators (TCI), which host multiple surface Dirac cones depending on the surface termination and the symmetries it preserves. This confinement is most dramatically reflected in the flux dependence of these Dirac states in the nanowire geometry, where different facets connect to form a closed surface. Using SnTe as a case study, we show how wires with all four facets of the <100> type display pronounced and unique Aharonov-Bohm oscillations, while nanowires with the four facets of the <110> type such oscillations are absent due to strong confinement of the Dirac states to each facet separately. Our results place TCI nanowires as a versatile platform for confining and manipulating Dirac surface states.

RMS and RI are supported by The Israel Science Foundation grant no. 1790/18. RI is also supported by the BSF grant no. 2018226. FJ acknowledges funding from the Spanish MCI/AEI/FEDER through grant PGC2018- 101988-B-C2. HB acknowledges support from the European Research Council (ERC-StG no. 678702, “TOPO-NW”).