Highly accurate semiclassical strong-field Herman-Kluk propagator method for high-harmonic generation

TL;DR

This paper introduces a semiclassical Herman-Kluk propagator method for high-harmonic generation that achieves near-exact accuracy by combining classical trajectories with quantum coherence, enabling efficient and precise simulations.

Contribution

The paper extends the semiclassical Herman-Kluk propagator to accurately model high-harmonic generation, matching exact quantum results and allowing efficient parallel computation.

Findings

Achieves near-identical results to exact quantum solutions for HHG.

Provides detailed analysis of the method's application to HHG.

Enables efficient parallel computation of classical trajectories.

Abstract

We extend our recently developed semiclassical strong-field Herman-Kluk propagator (SFHK) method to calculate high-order harmonic generation (HHG) for atoms in intense lasers. We show that our method, based on a combination of the Herman-Kluk propagator and the strong-field approximation, can provide highly accurate results for both HHG yield and phase, nearly identical to those from the exact numerical solutions of the time-dependent Schr\"odinger equation. We provide detailed analyses of our method and its applications to the HHG process, particularly the recombination time. The main computational task in this method is to solve the classical Newton equations for the active electron in the combined atomic potential and laser-electron interaction. The motion of the centers of the electron wave packets, modeled by coherent states, is governed by independent classical trajectories so that the computation can therefore be parallelized very efficiently.