Abstract

Recent advance in generation of strong electric fields in the mid-infrared to terahertz regions triggers research on extremely fast electron transportation in crystalline solids with terahertz to petahertz frequencies and associated high harmonic generation (HHG) in the spectral regions from visible to vacuum ultraviolet beyond typical bandgaps of solids [1, 2]. So far, most of the experiments choose a specific direction, along which the ballistic transportation of electron wavepackets is considered as a radiation source. However a one-dimensional model is not suitable to investigate polarization property of solid high harmonics. Recently, Berry curvature is introduced in a single-particle band to explain the generation of orthogonally polarized even harmonics from intraband current of hexagonal mono-layer MoS₂ [3].

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