Fermi polaron laser in two-dimensional semiconductors

TL;DR

This paper investigates how driven two-dimensional semiconductors can exhibit a Fermi polaron laser, where many-body interactions and stimulated scattering lead to coherent light emission with reduced linewidth.

Contribution

It introduces the concept of a Fermi polaron laser in 2D semiconductors, highlighting the role of many-body dressing and stimulated scattering in achieving lasing.

Findings

Stimulated scattering causes a superlinear increase in light emission.

Attractive polarons accumulate at the light-cone edge, enabling lasing.

Linewidth can be reduced below the nonradiative lifetime limit.

Abstract

We study the relaxation dynamics of driven, two-dimensional semiconductors, where itinerant electrons dress optically pumped excitons to form two Fermi-polaron branches. Repulsive polarons excited around zero momentum quickly decay to the attractive branch at high momentum. Collisions with electrons subsequently lead to a slower relaxation of attractive polarons, which accumulate at the edge of the light-cone around zero momentum where the radiative loss dominates. The bosonic nature of exciton polarons enables stimulated scattering, which results in a lasing transition at higher pump power. The latter is characterized by a superlinear increase of light emission as well as extended spatiotemporal coherence. As the coherent peak is at the edge of the light-cone and not at the center, the many-body dressing of excitons can reduce the linewidth below the limit set by the exciton nonradiative lifetime.