Quantum Simulations of Vibrational Strong Coupling via Path Integrals

TL;DR

This paper presents a quantum simulation method using thermostatted ring-polymer molecular dynamics to study vibrational strong coupling in liquids, revealing quantum effects on linewidths but not on Rabi splitting or dielectric constants.

Contribution

It introduces a novel quantum simulation approach for vibrational strong coupling in liquids using path integral methods, providing insights into quantum effects on polaritonic properties.

Findings

Quantum effects broaden polaritonic linewidths by about two times.

Quantum and classical simulations agree on Rabi splitting.

Static dielectric constant remains largely unchanged under VSC in simulations.

Abstract

A quantum simulation of vibrational strong coupling (VSC) in the collective regime via thermostatted ring-polymer molecular dynamics (TRPMD) is reported. For a collection of liquid-phase water molecules resonantly coupled to a single lossless cavity mode, the simulation shows that, as compared with a fully classical calculation, the inclusion of nuclear and photonic quantum effects does not lead to a change in the Rabi splitting but does broaden polaritonic linewidths roughly by a factor of two. Moreover, under thermal equilibrium, both quantum and classical simulations predict that the static dielectric constant of liquid water is largely unchanged inside versus outside the cavity. This result disagrees with a recent experiment demonstrating that the static dielectric constant of liquid water can be resonantly enhanced under VSC, suggesting either limitations of our approach or perhaps other experimental factors that have not yet been explored.