Role of virtual band population for high harmonic generation in solids

Abstract

We study the sub-band-gap high harmonic generation (HHG) in a methylammonium lead trichloride single crystal. Anisotropy in the crystal orientation dependence of the high harmonic yield is observed, and the yield varies substantially with the electric field strength of the midinfrared laser pulse used for excitation. Our real-time ab initio simulations reproduce the experimental results well and also show that the HHG is independent of the interband decoherence time. Based on a microscopic analysis of the intraband current, we reveal that the orientation dependence of the HHG in this perovskite semiconductor is governed by the virtual band population, rather than the anharmonicity of the electronic band structure.