Speaker: Rafael Molina
Affiliation: Instituto de Estructura de la Materia, CSIC
Date: Wednesday, 28 September 2016 at 13:00
Location: Seminar Room, Serrano 121 (CFMAC)
Topological semimetals are exciting new materials whose discovery became possible thanks to the refined understanding of exotic phenomena in topological band theory. We investigate the development of novel surface states when 3D Dirac or Weyl semimetals are placed under circularly polarized electromagnetic radiation. We find that the hybridization between inverted Floquet bands opens, in general, a gap, which closes at so-called exceptional points found for complex values of the momentum. This corresponds to the appearance of midgap surface states in the form of evanescent waves decaying from the surface exposed to the radiation. We observe a phenomenon reminiscent of Landau quantization by which the midgap surface states get a large degeneracy proportional to the radiation flux traversing the surface of the semimetal. We show that all of these surface states carry angular current, leading to an angular modulation of their charge that rotates with the same frequency of the radiation, which should manifest in the observation of a macroscopic chiral current in the irradiated surface.
Reference:
J. González, R.A. Molina, PRL 116, 156803 (2016).