Investigating high harmonic yield from different alignments of WSe2 semiconductor

This paper theoretically investigates high harmonic generation from a monolayer WSe2 driven by a laser pulse with different alignments, in-plane and out-of-plane polarizations. Our simulations are performed in the framework of the time-dependent density functional theory. Analysis of the dependence of the cutoff energy on the laser field strength shows that the cutoff energy increases linearly/quadratically with the increase of the electric field strength for the out-of-plane/in-plane laser field. Also, the wavelength dependence of high har-monic yield exhibits a sharp decrease with a rate of lambda-10 for the in-plane laser field, and a more gradual decline with a rate of lambda-4.75 for the out-of-plane laser field. These wavelength dependencies are explained by the tunneling rate and the spatial spread of electron wave-packet due to propagation in time and space. Additionally, it is demonstrated that the maximum harmonic yield is obtained when the in-plane laser is aligned along the armchair direction, or when the out-of-plane laser is polarized at a 20 degrees angle relative to the normal axis of the monolayer plane.