Role of virtual band population for high harmonic generation in solids


Yasuyuki Sanari, Hideki Hirori, Tomoko Aharen, Hirokazu Tahara, Yasushi Shinohara, Kenichi L. Ishikawa, Tomohito Otobe, Peiyu Xia, Nobuhisa Ishii, Jiro Itatani, Shunsuke A. Sato, and Yoshihiko Kanemitsu

We study sub-bandgap high harmonic generation (HHG) from a single crystal of perovskite semiconductor, methylammonium lead chloride (MAPbCl_3), which has strong and anisotropic optical nonlinearity. We observed anisotropy in the crystal orientation dependence of the high harmonics yield, which in turn varies substantially with the electric field strength of mid-infrared laser pulse for excitation. Our real-time ab initio simulations well reproduce the experimental results. From decomposition analysis of the intraband current, we reveal that strongly nonlinear virtual population dynamics, causing no permanent excited carriers, rather than the anharmonic potential in the band structure is mainly responsible for HHG.

Physical Review B :