High-harmonic generation approaching the quantum critical point of strongly correlated systems

TL;DR

This study investigates high-harmonic generation in strongly correlated systems near quantum critical points, revealing enhanced HHG and potential for topological phase distinction using nonlinear optics under strong laser fields.

Contribution

It demonstrates that systems near quantum critical points exhibit increased HHG and proposes using harmonic signals to distinguish topological phases, advancing ultrafast light sources and quantum phase studies.

Findings

HHG is more significant near the quantum critical point.

External fields near QCP induce more optical transition channels.

Harmonic components can distinguish topological from ordered phases.

Abstract

By employing the exact diagonalization method, we investigate the high-harmonic generation (HHG) of the correlated systems under the strong laser irradiation. For the extended Hubbard model on a periodic chain, HHG close to the quantum critical point (QCP) is more significant compared to two neighboring gapped phases (i.e., charge-density-wave and spin-density wave states), especially in low-frequencies. We confirm that the systems in the vicinity of the QCP are supersensitive to the external field and more optical-transition channels via excited states are responsible for HHG. This feature holds the potential of obtaining high-efficiency harmonics by making use of materials approaching to QCP. Based on two-dimensional Haldane model, we further propose that the even- or odd-order components of generated harmonics can be promisingly regarded as spectral signals to distinguish the topologically ordered phases from locally ordered ones. Our findings in this work pave the way to achieve ultrafast light source from HHG in strongly correlated materials and to study quantum phase transition by nonlinear optics in strong laser fields.