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Quantum phases of disordered three-dimensional Majorana-Weyl fermions
April 14, 20174:00 pm – 5:00 pm (CDT)

Quantum phases of disordered three-dimensional Majorana-Weyl fermions


Justin Wilson (Caltech)


Ar. Abanov



Mitchell Institute for Fundamental Physics & Astronomy

College Station, Texas 77843

Event Details

The gapless Bogoliubov-de Gennes (BdG) quasiparticles of a clean three-dimensional spinless p+ip superconductor provide an intriguing example of a thermal Hall semimetal (ThSM) phase of Majorana-Weyl fermions in class D of the Altland-Zirnbauer symmetry classification; such a phase can support a large anomalous thermal Hall conductivity and protected surface Majorana-Fermi arcs at zero energy. We study the effect of quenched disorder on such a topological phase with both numerical and analytical methods. Using the kernel polynomial method, we compute the average and typical density of states for the BdG quasiparticles; based on this, we construct the disordered phase diagram. We show for infinitesimal disorder, the ThSM is converted into a diffusive thermal Hall metal (ThDM) due to rare statistical fluctuations. Consequently, the phase diagram of the disordered model only consists of ThDM and thermal insulating phases. Nonetheless, there is a cross-over at finite energies from a ThSM regime to a ThDM regime, and we establish the scaling properties of the avoided quantum critical point which marks this cross-over. Additionally, we show the existence of two types of thermal insulators: (i) a trivial thermal band insulator (ThBI) [or BEC phase] supporting only exponentially localized Lifshitz states (at low energy), and (ii) a thermal Anderson insulator (AI) at large disorder strengths. We determine the nature of the two distinct localization transitions between these two types of insulators and ThDM.

Based on arXiv:1612.05648

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