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 selfinteracting 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 gapped photon mode, a different massless and slightly damped excitation appears. Strikingly, at low energies, this excitation has a linear dispersion and it propagates with the same velocity as the electrons, while at energies well above the electronhole 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 a certain momentum in the direction perpendicular to the separation of the Weyl nodes above which this gapless mode enters into an overdamped regime. Regarding the unscreened gauge field, we show that it is also attenuated, which is a nontopological property shared by Dirac semimetals as well.
 Publication:

Physical Review B
 Pub Date:
 May 2016
 DOI:
 10.1103/PhysRevB.93.195154
 arXiv:
 arXiv:1509.00248
 Bibcode:
 2016PhRvB..93s5154F
 Keywords:

 Condensed Matter  Mesoscale and Nanoscale Physics;
 High Energy Physics  Theory
 EPrint:
 Phys. Rev. B 93, 195154 (2016)