Adiabatic approach for high harmonic generation in solids induced by intense low-frequency pulses

TL;DR

The paper addresses high harmonic generation in solids driven by intense low-frequency pulses, where multiband dynamics complicate analytical understanding. It introduces an analytic adiabatic framework based on accelerated Bloch (Houston) states to treat laser–solid interactions nonperturbatively, deriving closed-form expressions for laser-dressed states and the HHG amplitude. The analysis shows interband polarization as the dominant HHG mechanism in the regime $|E_n-E_{n'}|\gg \omega$, and yields a factorized current $\mathbf J(\Omega)=\Omega\sum_s\sum_{n\neq 0} c^{(\rm tun)}_{n0,s} c^{(\rm pr)}_{n0,s} \mathbf D_{0n}(\mathbf K_s)$ that cleanly separates tunneling, propagation, and recombination steps, with the potential to extend to arbitrary numbers of bands. This work provides robust analytical insight into solid-state HHG, complementing numerical TDSE/SBE approaches and enabling rapid interpretation and design of solid-state attosecond sources under mid-IR driving fields.

Abstract

An analytic description of high harmonic generation (HHG) in solids induced by intense low-frequency pulses is presented within an adiabatic approach, which treats laser-matter interactions nonperturbatively. We derive the analytical expression for the laser-dressed state of an electron in an arbitrary spatially periodic potential, taking into account multiband structure of the solid target. Closed-form formulas for electron current and HHG spectra are presented. Based on the developed theory, we provide an analytic explanation for key features of HHG yield and show that the interband mechanism of HHG prevails over the intraband one.