Unconventional electromagnetic mode in neutral Weyl semimetals

Abstract

We study light propagation in a neutral Weyl semimetal with the Fermi level lying at the Weyl nodes in the weak self-interacting regime. The nontrivial topology induces a screening effect in one of the two transverse gauge fields, for which we find two branches of attenuated collective excitations. In addition to the known topologically gaped photon mode, a novel massless and slightly damped excitation appears. Strikingly, at low energies this new excitation has a linear dispersion and it propagates with the same velocity than the electrons, while at energies well above the electron-hole continuum threshold it behaves as a massive attenuated photon with velocity similar to the speed of light in the material. There is a crossover at certain momentum in the direction perpendicular to the separation of the Weyl nodes above which the novel gapless mode enters into an overdamped regime. Regarding the unscreened gauge field we show that it is also attenuated, which is a non-topological property shared by Dirac semimetals as well.

Giant tunable nonreciprocity of light in Weyl semimetals

“…Moreover, the AHE, CME, and corresponding photocurrents in WSs can be generated by illuminating with circularly polarized light [68,69,88]. Nontrivial topology of T -broken WSs also results in the chiral Fermi arc plasmons with hyperbolic isofrequency contours [82,83], in the chiral electromagnetic (EM) waves propagating at the vicinity of the magnetic domain wall in WSs [89], in the transverse EM waves in a static magnetic field (helicons) [90], and in the unusual EM modes with a linear dispersion in a neutral WS [79,80]. Besides, the AHE also makes the surface plasmon polaritons (SPPs) in WS chiral without applying an external magnetic filed (compare with Ref.…”

Dynamical correlation functions and the related physical effects in three-dimensional Weyl/Dirac semimetals

“…[ [45][46][47] and used to extensively investigate the plasmon excitations [47][48][49][50][51][52][53][54] and dynamics of phonons [55][56][57] in 3D Weyl/Dirac semimetals. The second kind is the chirality-dependent current-current correlation function…”

Anomalous Nernst and thermal Hall effects in tilted Weyl semimetals

“…A key feature that differentiates the time reversal breaking Weyl semimetal is the presence of a topological Chern-Simons term in its low-energy electromagnetic description. This term gives rise to many of the predicted exotic physical properties of Weyl semimetals, such as a finite quantum anomalous Hall response [14]; optical properties such as birefringence [25,26], circular dichroism [27], magnon electrodynamics [28], helicons [29], and the appearance of novel collective electromagnetic excitations [30,31]; and a new mechanism for the phonon Hall viscosity [32,33].…”