Effective attractive polariton-polariton interaction mediated by an exciton reservoir

We present a mechanism to endow the polariton gas with attractive interactions. The scheme relies on an exciton reservoir, which can be formed even if the excitons lie outside of the light cone. Such an attractive interaction should open different routes in the physics of quantum fluids, which we illustrate with a simple but nontrivial application whereby the polariton condensate enters the self-oscillation regime powered by the attraction from the reservoir. This results in pulsed emission in the GHz regime.

Figure 1

Integrals for electron, hole, and exciton exchange interactions (dashed lines), and their sum (solid line). The vertical dotted line separates the regions of repulsive and attractive interactions, providing the condition $\Delta Q{\lambda }_{2\text{D}}$ at which the character of the interaction reverses.

Figure 2

Integrals for electron (hole) and exciton exchange (direct) scattering (dashed lines), and their sum (solid line). This shows that the strength of the scattering processes is of the same order as compared to the strength of the polariton-polariton interaction.

Figure 3

Time evolution of (a) the polariton intensity $|{\psi }_0{|}^2$ and (b) the reservoir exciton intensity $|N_R|$. The interplay between attraction and repulsion bring the polariton emission into a self-oscillation regime.