Coherent dynamics in cavity femtochemistry: application of the multi-configuration time-dependent Hartree method

TL;DR

This study uses the multi-configuration time-dependent Hartree method to explore how molecular ensembles interact with cavity fields under femtosecond laser excitation, revealing superradiance, decoherence effects, and the impact of laser bandwidth on energy transfer.

Contribution

It applies a quantum dynamics approach to cavity femtochemistry, demonstrating how coherence, decoherence, and laser bandwidth influence energy transfer in molecular ensembles.

Findings

Superradiant energy transfer scales quadratically with molecule number.

Electronic decoherence reduces energy transfer, reverting to linear scaling.

Increasing laser bandwidth restores energy transfer efficiency regardless of molecule number.

Abstract

The photochemistry of a molecular ensemble coupled to a resonance cavity and triggered by a femtosecond laser pulse is investigated from a real-time, quantum dynamics perspective with the multi-configuration time-dependent Hartree method. Coherent excitation of a superposition of electronic states in the ensemble leads to superradiant energy transfer to the cavity characterized by quadratic scaling with the number of molecules. Electronic decoherence associated with loss of nuclear wave packet overlap among those states destroys superradiant energy transfer, returning to a linear regime. For equal pump laser conditions, the photoexcitation probability per molecule decreases with increase of the number of molecules inside the cavity. This is caused by a loss of resonance condition of the laser with the bright electronic-photonic states of the coupled cavity-ensemble system. Increase of the laser bandwidth restores the energy transferred per molecule and the trigger probability remains independent of the number of molecules in the cavity.