Multielectron interference of intraband harmonics in solids

High harmonic generation (HHG) in solids provides us compact and coherent extreme ultraviolet sources. However, the low yield of HHG is the bottleneck restricting its wide applications. We propose a pump-probe scheme to selectively enhance the yield of HHG. Our simulations illustrate abnormal harmonic yield dependence on the intensity of driving or preexcitation pulses. A multielectron interference model is proposed to reveal the mechanism of the extreme nonlinear optical phenomena. We find that the $k$-resolved intraband harmonic demonstrates different symmetry, phase, and amplitude, which can be observed by using a resonant preexcitation pulse. The position of the interference minimum obtained by solving the semiconductor Bloch equations agrees well with that obtained by our $k$-resolved semiclassical model. This interference model can help us probe the $k$-resolved band structure and optimize the ultrafast electron-hole dynamics for solid harmonic processes.