Cross-over from trion-hole to exciton-polaron in n-doped semiconductor quantum wells

Abstract

We present a theoretical study of photo-absorption in n-doped two-dimensional (2D) and quasi-2D semiconductors that takes into account the interaction of the photocreated exciton with Fermi-sea (FS) electrons through (i) Pauli blocking, (ii) Coulomb screening, and (iii) excitation of FS electron-hole pairs---that we here restrict to one. The system we tackle is thus made of one exciton plus zero or one FS electron-hole pair. At low doping, the system ground state is predominantly made of a "trion-hole"---a trion (two opposite-spin electrons plus a valence hole) weakly bound to a FS hole---with a small exciton component. As the trion is poorly coupled to photon, the intensity of the lowest absorption peak is weak; it increases with doping, thanks to the growing exciton component, due to a larger coupling between 2-particle and 4-particle states. Under a further doping increase, the trion-hole complex is less bound because of Pauli blocking by FS electrons, and its energy increases. The lower peak then becomes predominantly due to an exciton dressed by FS electron-hole pairs, that is, an exciton-polaron. As a result, the absorption spectra of $n$-doped semiconductor quantum wells show two prominent peaks, the nature of the lowest peak turning from trion-hole to exciton-polaron under a doping increase. Our work also nails down the physical mechanism behind the increase with doping of the energy separation between the trion-hole peak and the exciton-polaron peak, even before the anti-crossing, as experimentally observed.

20 pages, 10 figures

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Cited by in corpus (35)

• Control of the Exciton Radiative Lifetime in van der Waals Heterostructures
• Gate tunable dark trions in monolayer WSe${}_2$
• Optical properties of charged excitons in two-dimensional semiconductors
• Interacting Polaron-Polaritons
• Valley-selective chiral phonon replicas of dark excitons and trions in monolayer WSe2
• Theory of exciton-electron scattering in atomically thin semiconductors
• Multipath optical recombination of intervalley dark excitons and trions in monolayer WSe${}_2$
• Electron-exciton interactions in the exciton-polaron problem
• Nonlinear quantum optics with trion-polaritons in 2D monolayers: conventional and unconventional photon blockade
• Hexcitons and oxcitons in monolayer WSe${}_2$
• Observation of Rydberg moiré excitons
• Autoionization and dressing of excited excitons by free carriers in monolayer WSe2
• Attractive and repulsive exciton-polariton interactions mediated by an electron gas
• Landau-quantized excitonic absorption and luminescence in a monolayer valley semiconductor
• Many-body theory of optical absorption in doped two-dimensional semiconductors
• Electron recoil effect in electrically tunable MoSe2 monolayers
• Tunable optical nonlinearity for TMD polaritons dressed by a Fermi sea
• Many-body exciton and inter-valley correlations in heavily electron-doped WSe${}_2$ monolayers
• Enhanced scattering between electrons and exciton-polaritons in a microcavity
• Microscopic model of the doping dependence of line widths in monolayer transition metal dichalcogenides
• Composite excitonic states in doped semiconductors
• Microscopic theory of exciton and trion polaritons in doped monolayers of transition metal dichalcogenides
• Variationally optimized orbital approach to trions in two-dimensional materials
• Emergence of 6-particle "hexciton'' states in WS${}_2$ and MoSe${}_2$ monolayers
• Excitonic theory of doping-dependent optical response in atomically thin semiconductors
• Computational methods for 2D materials modelling
• Excitons and trions in monolayer semiconductors with correlated electrons
• Trion clustering structure and binding energy in 2D semiconductor materials: Faddeev equations approach
• Interplay of valley polarized dark trion and dark exciton-polaron in monolayer WSe2
• Nonlinear optical response of resonantly driven polaron-polaritons
• Trion formation resolves observed peak shifts in the optical spectra of transition metal dichalcogenides
• Excitons and trions in CrSBr bilayers
• Energy shifts and broadening of excitonic resonances in electrostatically-doped semiconductors
• Excitonic Bose-polarons in electron-hole bilayers
• Brightening interlayer excitons by electric-field-driven hole transfer in bilayer WSe2