RQMP Research Seminar

Fermi Polarons in 2D semiconductors

Francesca Marchetti

Universidad Autómona de Madrid

The concept of “impurity problem” in quantum physics, i.e., few particles surrounded by a quantum gas, goes back to 1933, when the Russian physicist Lev Landau described the properties of conduction electrons in a dielectric medium. Here, polarons are quasi-particles resulting from the dressing of electrons by collective excitations of the dielectric medium. Despite nearly a century of work, the polaron problem continues to attract significant interest. In particular, recent ground-breaking experiments in ultracold atomic gases and semiconductor TMD monolayers have renewed interest in this topic. This seminar focuses on the properties of Fermi polarons in 2D semiconductors, the elementary optical excitations of a 2D electron (or hole) gas. These systems have the unique possibility of being embedded into optical cavities to allow strong coupling between matter and light, leading to the formation of polaritonic quasi-particles. After reviewing the literature, I will describe our recent results in this area [A. Tiene et al., arXiv:2109.12994]. These consider the limit where the TMD monolayer is spin/valley polarised and the carriers in the Fermi sea are indistinguishable from one of the two carriers forming the optically generated exciton.