Topological valley and charge pumping in multi-Weyl semimetals

Abstract

We investigate the topological pumping effect in multi-Weyl semimetals, modulated by two orthogonal ac electric fields. In order to investigate the influence of the anisotropic energy–momentum relation on the pumping, we consider two different electric field configurations, i.e., (I) the electric fields along x and y directions, and (II) along y and z directions. It is found that both in the two configurations, there appear a pumping current in the direction perpendicular to electric field plane, whose direction is determined by the chirality, and the amount of the Weyl fermions pumped per cycle is given by the monopole charges. This indicates that the pumping effect is isotropic though the energy dispersion is anisotropic. Because the Weyl points of opposite chiralities always come in pairs in Weyl semimetals, the total particle current is vanishing, the pump giving rise to a net valley current. However, by using a valley-polarized electrode, one Weyl valley will be suppressed, and a charge current could be measured.