Effect of optically-induced potential on the energy of trapped exciton-polaritons below the condensation threshold

TL;DR

This study investigates how optically-induced potentials influence the energy of trapped exciton-polaritons below the condensation threshold, revealing that energy blueshifts are mainly caused by interactions with the excitonic reservoir rather than polariton-polariton interactions.

Contribution

It provides evidence that energy blueshifts in optically trapped polaritons are primarily due to reservoir interactions, challenging previous interpretations of strong polariton-polariton interactions.

Findings

Blueshifts increase with laser pump power.

Energy shifts are mainly due to reservoir reshaping.

Polariton-polariton interactions are not the primary cause.

Abstract

Exciton-polaritons (polaritons herein) offer a unique nonlinear platform for studies of collective macroscopic quantum phenomena in a solid state system. Shaping of polariton flow and polariton confinement via potential landscapes created by nonresonant optical pumping has gained considerable attention due to the degree of flexibility and control offered by optically-induced potentials. Recently, large density-dependent energy shifts (blueshifts) exhibited by optically trapped polaritons at low densities, below the bosonic condensation threshold, were interpreted as an evidence of strong polariton-polariton interactions [Nat. Phys. 13, 870 (2017)]. In this work, we further investigate the origins of these blueshifts in optically-induced circular traps and present evidence of significant blueshift of the polariton energy due to reshaping of the optically-induced potential with laser pump power. Our work demonstrates strong influence of the effective potential formed by an optically-injected excitonic reservoir on the energy blueshifts observed below and up to the polariton condensation threshold and suggests that the observed blueshifts arise due to interaction of polaritons with the excitonic reservoir, rather than due to polariton-polariton interaction.