Many-Body Theory of Trion Absorption Features in Two-Dimensional Semiconductors

Abstract

Recent optical studies of monolayer transition metal dechalcogenides have demonstrated that their excitonic absorption feature splits into two widely separated peaks at finite carrier densities. The additional peak is usually attributed to the presence of trions, bound states of two electrons and a hole or an electron and two holes. Here we argue that in the density range over which the trion peak is well resolved, it cannot be interpreted in terms of weakly coupled three-body systems, and that the appropriate picture is instead one in which excitons are dressed by interactions with a Fermi sea of excess carriers. This coupling splits the exciton spectrum into a lower energy attractive exciton-polaron branch, normally identified as a trion branch, and a higher energy repulsive exciton-polaron branch, normally identified as an exciton branch. We have calculated the frequency and doping dependence of the optical conductivity and found that: (i) the splitting varies linearly with the Fermi energy of the excess quasiparticles; (ii) the trion peak is dominant at high carrier densities; (iii) and the trion peak width is considerably smaller than that of the excitonic peak. Our results are in good agreement with recent experiments.

11 pages and 8 figures. Extended version accepted to Physical Review B

References in corpus (8)

• Electric Field Effect in Atomically Thin Carbon Films
• The electronic properties of graphene
• Exciton Binding Energy of Monolayer WS2
• Exciton band structure of monolayer MoS2
• Three-particle Complexes in Two-Dimensional Semiconductors
• Excitons and Optical Absorption on the Surface of a Strong Topological Insulator with a Magnetic Energy Gap
• Many-body effects of a two-dimensional electron gas on trion-polaritons
• Single particle polariton properties in doped quantum well microcavities: role of the Fermi edge singularity and Anderson orthogonality catastrophe

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• Many-body theory of optical absorption in doped two-dimensional semiconductors
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