Enhanced high-order harmonics through periodicity breaks: From backscattering to impurity states

Backscattering of delocalized electrons has been recently established [Phys. Rev. A 105, L041101 (2022)] as a mechanism to enhance high-order harmonic generation (HHG) in periodic systems with broken translational symmetry. Here we study this effect for a variable spatial gap in an atomic chain. Propagating the many-electron dynamics numerically, we find enhanced HHG and identify its origin in two mechanisms, depending on the gap size, either backscattering or enhanced tunneling from an impurity state. Since the gapped atomic chain exhibits both impurities and vacancies in a unified setting, it provides insight into how periodicity breaks influence HHG in different scenarios.

Automated summary

Backscattering of delocalized electrons has been found to enhance high-order harmonic generation in periodic systems with broken translational symmetry. This study explores the effect of variable spatial gaps in an atomic chain and identifies two mechanisms, backscattering and enhanced tunneling from an impurity state, that contribute to the enhanced harmonic generation.