High-harmonic generation in a quantum electron gas trapped in a nonparabolic and anisotropic well

TL;DR

This paper presents a quantum hydrodynamics-based model to study high-harmonic generation in an anisotropic, nonparabolic quantum well, revealing chaos as a key factor and demonstrating efficient harmonic excitation with chirped waves.

Contribution

The paper introduces a self-consistent six-equation quantum hydrodynamics model capturing nonlinear and quantum effects in anisotropic quantum wells for high-harmonic generation.

Findings

High harmonic generation correlates with chaos in phase space.

Chirped electromagnetic waves efficiently excite higher harmonics.

The model predicts nonlinear dynamics leading to harmonic generation.

Abstract

An effective self-consistent model is derived and used to study the dynamics of an electron gas confined in a nonparabolic and anisotropic quantum well. This approach is based on the equations of quantum hydrodynamics, which incorporate quantum and nonlinear effects in an approximate fashion. The effective model consists of a set of six coupled differential equations (dynamical system) for the electric dipole and the size of the electron gas. Using this model we show that: (i) High harmonic generation is related to the appearance of chaos in the phase space, as attested by related Poincar\'e sections; (ii) Higher order harmonics can be excited efficiently and with relatively weak driving fields by making use of chirped electromagnetic waves.