Macroscopic degeneracy of zero-mode rotating surface states in 3D Dirac and Weyl semimetals under radiation

Abstract

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 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.

5 pages + supplemental material

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• Surface and 3D quantum Hall effects from engineering of exceptional points in nodal-line semimetals
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• Generating surface states in a Weyl semi-metal by applying electromagnetic radiation
• Electric field manipulation of surface states in topological semimetals
• Localization length versus level repulsion in 1-D driven disordered quantum wires
• Effect of the external fields in high Chern number quantum anomalous Hall insulators
• Floquet boundary states in AB-stacked graphite
• Photoprotected spin Hall effect on graphene with substrate induced Rashba spin-orbit coupling
• Transition between anomalous and Anderson localization in systems with non-diagonal disorder driven by time-periodic fields
• Floquet second-order topological insulator in strained graphene
• Spectroscopic Signatures of a Liouvillian Exceptional Spectral Phase in a Collective Spin