Valley-dependent conductivity and dispersion relation of surface magnetoplasmons

Abstract

Electron hydrodynamics attracts increasing interest in solid state physics, offering a universal long-wavelength description of collective modes in a two-dimensional system. In two-dimensional materials with broken inversion symmetry and two degenerate valleys, a perpendicular magnetic field lifts the valley degeneracy via a Zeeman effect due to the orbital magnetic moments arising from electron rotations, relevant for developing valleytronic devices. In this work, we use a two-component hydrodynamic model to investigate the valley-dependent conductivity tensor and valley-dependent dispersion relation of surface magnetoplasmons under the modulations of the perpendicular magnetic field, Berry curvature and topological orbital magnetic moment. It is shown that the valley splitting of conductivity is large and tunable in the presence of the valley Zeeman effect. Valley splitting of frequency appears on the order of terahertz, which is preferable for realizing sub-wavelength nonreciprocal magneto-optical devices in the terahertz range.