Two-Mode Floquet Fewest Switches Surface Hopping for Nonadiabatic Dynamics Driven by Two-Frequency Laser Fields

TL;DR

This paper introduces a new two-mode Floquet surface hopping method for simulating nonadiabatic molecular dynamics driven by two-frequency laser fields, validated against exact calculations and suitable for designing control protocols.

Contribution

The paper develops and validates a novel two-mode Floquet F-FSSH approach for two-frequency laser-driven nonadiabatic dynamics within a mixed quantum-classical framework.

Findings

Good agreement with exact results across various models.

Effective for simulating two-frequency laser control protocols.

Establishes a practical framework for future experimental applications.

Abstract

Two-frequency (two-color) laser fields provide a powerful and flexible means for steering molecular dynamics. However, quantitatively reliable and scalable theoretical tools for simulating laser-driven nonadiabatic processes under such fields remain limited. Here, we develop a two-mode Floquet fewest switches surface hopping (two-mode F-FSSH) approach for two-frequency driving within a mixed quantum-classical framework. We validate the algorithm on three driven one-dimensional two-state models: a Rabi model and two avoided-crossing scattering models. The electronic and nuclear dynamics are benchmarked against numerically exact results from split-operator calculations, showing good agreement across a broad range of field parameters and initial conditions. These results establish two-mode F-FSSH as a practical framework for simulating and designing two-frequency control protocols and motivate extensions to more realistic experimental settings.