Splitting the hinge mode of higher-order topological insulators

Raquel Queiroz, Ady Stern

Published 2018-07-11Version 1

We study the effect of the coupling of a helical mode at the hinges of an intrinsic higher order topological insulator (HOTI) to a proximate ferromagnet and to a proximate s-wave superconductor. We find that in contrast to the helical modes at the edges of a two dimensional topological insulator, which are gapped by these couplings, the helical one-dimensional hinge modes generically remain gapless and spatially split. The ferromagnet turns the helical mode into a chiral mode that surrounds the magnetized region, and the superconductor, when strong enough, turns that mode to two helical Majorana modes that surround the superconducting region. The induced superconductor at the surface of a HOTI comprises a two dimensional, time-reversal invariant, topological superconductor. We propose that this state can be measured in electrical transport by an extension of previously proposed interferometry experiments.