Significant photothermoelectric effect of topological semimetals at infrared bands

We theoretically explore the photothermoelectric effect (PTE) of topological semimetals using the static two-temperature model. The interaction between the Dirac or Weyl fermions and electromagnetic waves is described by the dielectric constant in the model Hamilton of topological semimetals. Numerical calculations predict a significant PTE in the conventional plasmon mode with infrared bands of both the Dirac and Weyl semimetals. In addition to the PTE with a plasmon mode, the Weyl semimetals exhibit an enormous PTE at the frequencies of the two unconventional modes (helicon waves) in the infrared region. The helicon-wave modes originate from the resonant coupling between left- and right-circularly polarized electromagnetic waves and the helical motion of Weyl electron under an effective magnetic field induced by the Berry curvature. The frequencies of the helicon-wave modes depend on the carrier concentration, the Fermi velocity, and the distance between the positive and negative Weyl points in the Weyl semimetals, as well as the transport lifetime of the Weyl fermion. Using real parameters for the topological semimetals, we propose ideal materials for detecting the specific infrared bands of electromagnetic waves. This work strongly suggests that topological semimetals are promising for detecting electromagnetic waves in the infrared region, taking advantage of their significant PTE.