Light interactions with polar quantum systems

TL;DR

This paper explores the complex dynamics of polar quantum systems with permanent dipoles interacting with classical fields in the ultrastrong coupling regime, simplifying analysis through a new reference frame and revealing nonlinear interaction scaling.

Contribution

It introduces a Jaynes-Cummings-like model with effective parameters for polar systems in the ultrastrong coupling regime, enabling simplified analysis and revealing nonlinear scaling of interaction strength.

Findings

Dynamics can be described in a dynamic reference frame.

Derived a Jaynes-Cummings-like framework with effective parameters.

Interaction strength scales nonlinearly with field amplitude.

Abstract

We investigate the dynamics of polar systems coupled to classical external beams in the ultrastrong coupling regime. The permanent dipole moments (PDMs) sustained by polar systems can couple to the electromagnetic field, giving rise to a variety of processes such as difference-frequency and harmonic generation, reflected in complicated dynamics of the atomic system. Here, we demonstrate that the dynamics can be described simply in a dynamic reference frame. We derive a Jaynes-Cummings-like framework with effective parameters describing frequency shift, coupling strength with the driving field, and a rescaled relaxation rate. The familiar linear scaling of the interaction strength with the field amplitude is replaced with a nonlinear dependence, suggesting potential applications for improving the coherence of quantum system ensembles with permanent dipoles.