Dressed atom versus exciton polariton: From Rabi oscillations to the Fermi Golden rule

TL;DR

This paper unifies the description of dressed atoms and exciton polaritons, showing how their photon dynamics transition from oscillations to exponential decay as excited state lifetime decreases, revealing a Fermi Golden rule-like decay process.

Contribution

It provides a unified analytical framework for dressed atom and exciton polariton systems, clarifying their differences and the transition from Rabi oscillations to decay.

Findings

Photon number oscillates at Rabi frequency for long-lived states.

Photon number decays exponentially when excited state lifetime is short.

Decay follows a Fermi Golden rule-like process with a different energy conservation concept.

Abstract

We rederive the dressed atom and the exciton polariton within the {\it same} framework to make clear that their difference only comes from the number of electrons available for photoexcitations. Using it, we analytically show how the time dependence of the photon number transforms from an oscillating behavior (at the stimulated or vacuum Rabi frequency) to an exponential decay (identical for atom and semiconductor) when the excited state lifetime decreases. Although the matter ground state is in both cases coupled by monochromatic photons {\it not to a continuum but to a discrete state}, this decay yet follows a kind of Fermi Golden rule. The energy conservation it contains, is however conceptually different.