Observation of electrical high-harmonic generation

TL;DR

This paper reports the first observation of electrical high-harmonic generation up to the 300th order, revealing non-perturbative behavior and potential for exploring exotic quantum phenomena and ultra-fast electrical signals.

Contribution

It presents the experimental detection of high-order electrical HHG, demonstrating non-perturbative characteristics and theoretical insights into Berry curvature effects.

Findings

Electrical HHG observed up to 300th order

e-HHG exhibits non-perturbative oscillatory behavior

Theoretical models suggest Berry curvature contributions

Abstract

High-harmonic generation (HHG), an extreme nonlinear effect, introduces an unprecedented paradigm to detect emergent quantum phases and electron dynamics inconceivable in the framework of linear and low-order nonlinear processes. As an important manifestation, the optical HHG (o-HHG) enables extraordinary opportunities to underpin attosecond physics. In addition to nonlinear optics, emerging nonlinear electric transport has been demonstrated recently and opens new paradigms to probe quantum phase transition, symmetry breaking, band geometrical and topological properties. Thus far, only electrical second-/third-harmonic generation in perturbative regime has been elucidated, while the electrical HHG (e-HHG) that can advance to extreme non-perturbative physics remains elusive. Here we report the observation of e-HHG up to 300th-order. Remarkably, the e-HHG shows a clear non-perturbative character and exhibits periodic oscillations with the reciprocal of driving current. Further, theoretical simulations corroborate the experiments, suggesting the contribution of singular distribution of Berry curvature near band edges. Our results demonstrate e-HHG in extreme nonlinear regime and may shed light on a plethora of exotic physics and applications, such as extreme non-equilibrium quantum phenomena, ultra-fast and coherent electrical signal generations and detections.