What Determines the Wave Function of Electron-Hole Pairs in Polariton Condensates?

TL;DR

This paper investigates how the wave function of electron-hole pairs in polariton condensates is influenced by tunable parameters, revealing a transition from Coulomb to photon-mediated binding and mapping the phase diagram of ground states.

Contribution

It provides a detailed analysis of the ground state transitions in polariton condensates considering experimental parameters, highlighting the change in binding mechanisms and phase behavior.

Findings

Transition from Coulomb to photon-mediated interactions as density increases

Formation of strongly bound pairs similar to Frenkel excitons in the photonic regime

Phase diagram outlining crossover and first-order transition regimes

Abstract

The ground state of a microcavity polariton Bose-Einstein condensate is determined by considering experimentally tunable parameters such as excitation density, detuning, and ultraviolet cutoff. During a change in the ground state of Bose-Einstein condensate from excitonic to photonic, which occurs as increasing the excitation density, the origin of the binding force of electron-hole pairs changes from Coulomb to photon-mediated interactions. The change in the origin gives rise to the strongly bound pairs with a small radius, like Frenkel excitons, in the photonic regime. The change in the ground state can be a crossover or a first-order transition, depending on the above-mentionsed parameters, and is outlined by a phase diagram. Our result provides valuable information that can be used to build theoretical models for each regime.