Correlation effects in high-harmonic generation from finite systems

Abstract

Using the Hubbard model we study how the process of high-order harmonic generation (HHG) is modified by beyond mean-field electron-electron correlation for both finite and bulk systems. A finite-size enhancement of the HHG signal is found and attributed to electrons backscattering off the lattice edges. Additionally, with increasing strength of the electron-electron correlation an enhancement of the high-frequency regime of the HHG spectrum is found. This is attributed to the on-site Coulomb repulsion between electrons giving rise to a localized quiver motion of the electrons. The finite-lattice enhancement dominates the HHG spectra from a few harmonic orders until a threshold from which the correlational enhancement dominates. This threshold is determined by the degree of correlation and decreases into the low-frequency regime for increasing electron-electron correlation. This infers that as the Mott insulator limit of high electron-electron correlation is approached, the finite-size effect on the electron dynamics becomes negligible.

Doping and gap-size dependence of high-harmonic generation in graphene : Importance of consistent formulation of light-matter coupling

“…However, in practice, these values may change with dopinglevel 26 or with temperatures due to the correlation effects 27,69,70 . Although recently the effects of correlations on HHG beyond the phenomenological description have been attracting much interest [70][71][72][73][74][75][76][77][78][79][80][81][82][83] , deeper understanding is required for further accurate understanding of behavior of HHG. This is an important future task.…”