DQMP Seminar - Emergence of massless Dirac and Weyl fermions in Semi-metals with broken PT symmetry

20.03.2018 13:00 – 14:30

The Weyl and Dirac semimetals are recently discovered topological quantum states of matter
characterized by the unavoidable crossing of two non- or doubly-degenerate energy bands
near the Fermi level, respectively. These crossing points (Weyl or Dirac nodes) are the source
of exotic phenomena, including the realization of massless Dirac and Weyl fermions as
quasiparticles in the bulk and the formation of Fermi arc states on the surfaces. An important
issue in the research of topological quantum states is to study the relationship between various
topological phases and the symmetries possessed by different systems. Using our recent
angle-resolved photoemission results I will show how the Weyl and Dirac semimetal phases
are realized in systems with broken inversion (P) and/or time-reversal (T) symmetry. I shall
also address the issue whether the band degeneracy can be retained when parity-time
symmetry is broken, which is essential for the emergence of massless Dirac fermions as lowenergy
excitations (quasiparticles) in the system.

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

entrée libre