# High-Harmonic Generation in a Correlated Electron System

## TL;DR

This paper demonstrates high-harmonic generation (HHG) arising from many-body electron dynamics in a correlated low-dimensional system, revealing new mechanisms beyond traditional band-structure explanations.

## Contribution

It introduces the emergence of HHG signals from many-body states in a correlated electron system, analyzed through a fermion and pseudo-spin model on a dimer lattice.

## Key findings

- HHG signals show threshold behavior with light amplitude.
- HHG is linked to tunneling and recombination of kink-antikink excitations.
- Charge density polarization influences HHG in the system.

## Abstract

High-harmonic generation (HHG) in crystalline solids have been examined so far on the basis of one-body energy-band structures arising from electron itineracy in a periodic potential. Here, we show emergence of HHG signals which are attributed to dynamics of many-body states in a low-dimensional correlated electron system. An interacting fermion model and its effective pseudo-spin model on a one-dimensional dimer-type lattice are analyzed. Observed HHG signals in a spontaneously symmetry-broken state, where charge densities are polarized inside of dimer units, show threshold behavior with respect to light amplitude and are interpreted in terms of tunneling and recombination of kink-antikink excitations in an electric field.