Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 11: Topology: Quantum Hall Systems

TT 11.2: Talk

Tuesday, September 6, 2022, 09:45–10:00, H10

Quantum Hall critical phase at topological insulator surfaces — •Johannes Dieplinger¹, Mateo Moreno-Gonzalez², Soumya Bera³, Martin Puschmann¹, Matthew Foster⁴, Ferdinand Evers¹, and Alexander Altland² — ¹University of Regensburg, Regensburg, Germany — ²Universiy of Cologne, Cologne, Germany — ³IIT Bombay, Mumbai, India — ⁴Rice University, Houston, Texas, USA

We show that an AIII three-dimensional topological insulator, when tuned away from the critical point at zero energy, realizes a finite class A critical phase on its surface, i.e. a continuum of quantum Hall critical states, instead of an naively expected quantum Hall insulator. Criticality is characterized numerically via an analysis of the multifractal exponents of the wave functions at the surface of the three dimensional bulk.

This numerical work supports a recently proposed first principle theory explaining the existence of the quantum Hall critical phase. Open questions remain concerning the nature of disordered surface states with higher topological index.