Strong-field-driven dynamics and high-harmonic generation in interacting 1D systems (Conference Presentation)

Abstract

The observation of high-order harmonic generation (HHG) from bulk crystals is stimulating substantial efforts to understand the involved mechanisms and their analogue to the intuitive three-step recollision model of gas phase HHG. On the technological side, efficient solid-state HHG is anticipated to enable compact attosecond and ultraviolet light sources that could unveil electron dynamics in chemical reactions and provide sharper tomographic imaging of molecular orbitals. Here we explore the roles of electronic band structure and Coulomb interactions in solid-state HHG by studying the optical response of linear atomic chains and carbon nanotubes to intense ultrashort pulses. Specifically, we simulate electron dynamics by solving the single-particle density matrix equation of motion in the presence of intense ultrafast optical fields, incorporating tight-binding electronic states and a self-consistent electron-electron interaction. While linear atomic chains constitute an idealized system, our realistic 1D model readily provides insight on the temporal evolution of electronic states in reciprocal space, both in the absence or presence of electron interactions, which we demonstrate to play an important role in the HHG yield. This model further predicts that doped semiconductors generate high harmonics more efficiently than their metallic and undoped counterparts. To complement this idealized system we also show results for HHG in more realistic quasi-1D structures such as carbon nanotubes, the behavior of which is found to be in good qualitative agreement with the atomic chains. Our findings apply directly to extreme nonlinear optical phenomena in atoms on surfaces, carbon-based structures, linear arrays of dopant atoms in semiconductors, and linear molecules, such as polycyclic aromatic hydrocarbon chains, and can be straightforwardly extended to optimize existing platforms for HHG or identify new solid-state alternatives in the context of nonlinear plasmonics.

Enhanced high-harmonic generation from chromium-doped magnesium oxide

“…Therefore, one can expect substantial changes of the HHG yield due to modifications of the band gap. This fact has recently raised interest among theoretical works on the use of doped materials for the HHG [26][27][28][29] . For instance, the effect of impurity levels on the HHG is discussed in the theoretical investigations exploiting time-dependent density functional theory 27 , where the authors have shown the enhanced HHG yield from the donor-doped material due to the electron tunneling from the impurity states to the conduction band.…”