Benchmarking mixed quantum-classical dynamics for collective electronic strong coupling

TL;DR

This paper benchmarks semi-classical quantum-classical methods against exact quantum simulations for modeling nonadiabatic dynamics of molecules under collective strong light-matter coupling, demonstrating their qualitative and quantitative reliability.

Contribution

It evaluates the accuracy of Ehrenfest and FSSH methods compared to MCTDH for collective electronic strong coupling, highlighting the effectiveness of FSSH with decoherence correction.

Findings

Semi-classical methods reproduce qualitative features of quantum dynamics.

FSSH with decoherence correction provides quantitative agreement.

Semi-classical approaches are computationally efficient alternatives to quantum simulations.

Abstract

Experiments indicate that collective coupling of molecular ensembles to confined optical modes can modify excited-state dynamics and photochemical reactivity. To describe such cavity-induced effects at atomic resolution, semi-classical molecular dynamics approaches have been developed that treat nuclear motion classically while describing the collective light-matter interaction within the Tavis-Cummings framework of quantum electrodynamics. Here, we benchmark mixed quantum-classical approaches, Ehrenfest dynamics and Fewest-Switches Surface Hopping (FSSH), for simulating nonadiabatic dynamics of electronically strongly coupled carbon monoxide molecules. Their predictions are compared against numerically exact quantum dynamics simulations performed with the multi-configuration time-dependent Hartree (MCTDH) method, which treats both electronic and nuclear degrees of freedom quantum mechanically. We find that the semi-classical approaches reproduce the qualitative features of the full quantum dynamics. Quantitative agreement is best achieved with FSSH when a decoherence correction is included. These results demonstrate that mixed quantum-classical methods provide a computationally efficient and quantitatively reliable alternative to fully quantum simulations for investigating nonadiabatic photochemistry under collective electronic strong coupling in systems beyond the reach of exact quantum treatments.