Higher harmonic generation by massive carriers in buckled two-dimensional hexagonal nanostructures

Abstract

Generation of high harmonics in novel two-dimensional (2D) nanostructures such as silicene, germanene, and stanene initiated by strong coherent electromagnetic radiation of arbitrary polarization, taking into account the spin-orbit coupling and the buckling of two Bravais lattices, is investigated. The buckled hexagonal lattice system is described by the four-band second-nearest-neighbor tight-binding model. The developed theory of the interaction of massive (nonzero effective mass) carriers with a strong driving wave field covers the full Brillouin zone of a 2D hexagonal nanostructure. The wave-matter interaction is taken in the length gauge that provides proper inclusion of inter- and intraband transitions with nonzero Berry curvatures. The closed set of differential equations for the single-particle density matrix of massive carriers is solved numerically. The obtained results show that novel 2D nanostructures can serve as an effective medium for the generation of even and odd high harmonics of arbitrary polarization. Moreover, for the nanostructures under consideration, the role of the band topology is significant at harmonic generation.