Effect of Disorder on Edge States in Nodal Topological Materials

Many nodal topological materials exhibit gapless flat-band boundary modes which are protected by non-trivial topology in momentum space. Here we ask the question of whether, as is the case for weak topological insulators [1], these boundary flat-bands maintain their integrity in the presence of disorder – and whether this leads to observable signatures in transport. To do this, we study the effects of various types of quenched short-range disorder on the energy spectrum, localization, and transport properties of the boundary states of a 2D topological semi-metal in symmetry class BDI. Our primary example is graphene with time-reversal and particle-hole symmetry. We discuss the implications of our results for experimentally detecting the boundary modes of nodal topological superconductors in 2D. References: [1] Z. Ringel, Y. E. Kraus, A. Stern, Phy. Rev. B, 86, 045102 (2012)