Non-adiabatic Dynamics in a Laser Field with Floquet Fewest Switches Surface Hopping: The Need for An Accurate Treatment of Coherence and Decoherence Remains

TL;DR

This paper compares two approaches for non-adiabatic dynamics in laser fields, demonstrating that Floquet-based surface hopping provides more accurate scattering predictions by properly accounting for coherence effects.

Contribution

It introduces and evaluates a Floquet-based surface hopping method, showing its superiority over traditional approaches in modeling laser-induced molecular dynamics.

Findings

F-FSSH predicts transmission and reflection more accurately.

F-FSSH correctly predicts final scattering momentum.

Accounting for Floquet state interference is crucial for accuracy.

Abstract

We investigate two well-known approaches for extending the fewest switches surface hopping (FSSH) algorithm to periodic time-dependent couplings. The first formalism acts as if the instantaneous adiabatic electronic states were standard adiabatic states, which just happen to evolve in time. The second formalism replaces the role of the usual adiabatic states by the time-independent adiabatic Floquet states. For a set of modified Tully model problems, the Floquet FSSH (F-FSSH) formalism gives a better estimate for both transmission and reflection probabilities than the instantaneous adiabatic FSSH (IA-FSSH) formalism. More importantly, only F-FSSH predicts the correct final scattering momentum. Finally, in order to use Floquet theory accurately, we find that it is crucial to account for the interference between Floquet states. Our results should be of interest to all those interested in laser induced molecular dynamics.