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TT: Fachverband Tiefe Temperaturen
TT 41: Quantum Transport and Quantum Hall Effects II (joint session HL/TT)
TT 41.6: Talk
Wednesday, March 29, 2023, 16:45–17:00, JAN 0027
Massless Dirac fermions on a space-time lattice with a topologically protected Dirac cone — •Michal Pacholski1, Alvaro Donís Vela3, Gal Lemut3, Jakub Tworzydlo2, and Carlo Beenakker3 — 1Max Planck Institute for the Physics of Complex Systems, Dresden, Germany — 2Warsaw University, Warsaw, Poland — 3Lorentz Institute, Leiden, The Netherlands
The symmetries that protect massless Dirac fermions from a gap opening may become ineffective if the Dirac equation is discretized in space and time, either because of scattering between multiple Dirac cones in the Brillouin zone (fermion doubling) or because of singularities at zone boundaries. Here we introduce an implementation of Dirac fermions on a space-time lattice that removes both obstructions. The quasi-energy band structure has a tangent dispersion with a single Dirac cone that cannot be gapped without breaking both time-reversal and chiral symmetries. We show that this topological protection is absent in the familiar single-cone discretization with a linear sawtooth dispersion, as a consequence of the fact that there the time-evolution operator is discontinuous at Brillouin zone boundaries.