Three-dimensional topological plasmons in Weyl semimetals

Our systematic studies on the topological aspects of plasmons of Weyl semimetals in the presence of a magnetic field have uncovered two types of three-dimensional (3D) topological plasmons: the bulk plasmons and the Fermi-arc plasmons over opposite surfaces. As a consequence of the bulk-boundary correspondence, there are unidirectional surface/edge plasmons whose directions and dispersions can be controlled by the external field. These chiral surface plasmons possess momentum-location lock and strong confinement of electromagnetic (EM) fields. The anomalous Hall conductivity brings about abundant anisotropic plasmon dispersions, from linear to parabolic or even hyperbolic bands. In addition, a semiclassical picture of electron motion is proposed to show the formation of Weyl orbits and the consequent effect on plasmons. Our work thus provides instructive insights into the electron dynamics and collective excitations of Weyl semimetals and suggests it is a good seed for 3D topological plasmonics.