Drag force of a exciton-polariton condensate under non-resonant pumping

TL;DR

This paper investigates how reservoir modes influence the superfluidity of non-resonantly pumped exciton-polariton condensates by analyzing the drag force on an impurity, revealing velocity-dependent behaviors and effects near phase transition.

Contribution

It provides the first theoretical analysis of drag force in non-resonantly pumped polariton condensates, highlighting the reservoir's impact on superfluid properties.

Findings

Drag force is large at low impurity velocities due to reservoir modes.

Drag force decreases as impurity velocity increases.

Near the phase transition, drag force resembles that of equilibrium superfluid.

Abstract

Exciton-polariton condensate in semiconductor microcavities constitute a novel kind of non-equilibrium superfluid. In a recent experiment [P. Stepanov, {\it et. al.,} Nat. Commun. {\bf 10}, 1038 (2019)], the dispersion relation of collective excitations in a polariton condensate under the resonant pumping has been investigated with the emphasis on the role of reservoir of long-lived excitons in determining the superfluidity. Inspired by such an experimental advance, we study the superfluidity of a exciton-polaritonn condensate under non-resonant pumping by calculating the drag force exerted on a classical impurity moving in a polariton condensate. For a non-resonant pumped polariton condensate prepared in the gapped phase, due to the reservoir's modes, the drag force can be large when the velocity of the impurity is small. Besides, as the velocity increases, the drag force can decrease. For not very large velocity, the drag force is enhanced if the condensate is tuned to be more dissipative. When the condensate is close to the transition point between the gapped phase and the gapless one, the drag force is similar to that of the equilibrium superfluid. Our present work reveals the effects of the reservoir's modes on the superfluidity properties of a polariton condensate with the non-resonant pumping.