Physical Review B - Condensed Matter and Materials Physics
We demonstrate how the nontrivial interplay between spin-orbit coupling and nodeless s-wave superconductivity can drive a fully gapped two-band topological insulator into a time-reversal invariant gapless topological superconductor supporting symmetry-protected Majorana flat bands. We characterize topological phase diagrams by a Z2×Z2 partial Berry-phase invariant, and show that, despite the trivial crystal geometry, no unique bulk-boundary correspondence exists. We trace this behavior to the anisotropic quasiparticle bulk gap closing, linear vs quadratic, and argue that this provides a unifying principle for gapless topological superconductivity. Experimental implications for tunneling conductance measurements are addressed, relevant for lead chalcogenide materials.
Deng, Shusa; Ortiz, Gerardo; Poudel, Amrit; and Viola, Lorenza, "Majorana Flat Bands in S -Wave Gapless Topological Superconductors" (2014). Open Dartmouth: Faculty Open Access Articles. 1930.