Signatures of Dimensionality and Symmetry in Exciton Bandstructure: Consequences for Time-Evolution

Abstract

Exciton dynamics, lifetimes and scattering are directly related to the exciton dispersion, or bandstructure. While electron and phonon bandstructures are well understood and can be easily calculated from first principles, the exciton bandstructure is commonly conflated with the underlying electronic bandstructure, where the exciton dispersion is assumed to follow the same dispersion as the electron and hole bands from which it is composed (i.e., the effective mass model). Here, we present a general theory of exciton bandstructure within both ab initio and model Hamiltonian approaches. We show that contrary to common assumption, the exciton bandstructure contains non-analytical discontinuities -- a feature which is impossible to obtain from the electronic bandstructure alone. These discontinuities are purely quantum phenomena, arising from the exchange scattering of electron-hole pairs. We show that the degree of these discontinuities depends on materials' symmetry and dimensionality, with jump discontinuities occurring in 3D and different orders of removable discontinuities in 2D and 1D. We connect these unexpected features to the early stages of exciton dynamics, which shows remarkable correspondence with recent experimental observations and suggests that the measured diffusion patterns are influenced by the underlying exciton bandstructure.

References in corpus (8)

• Nonlinear Photoluminescence in Atomically Thin Layered WSe2 Arising from Diffusion-Assisted Exciton-Exciton Annihilation
• Exciton-Phonon Interaction and Relaxation Times from First Principles
• Interlayer coupling and gate-tunable excitons in transition metal dichalcogenide heterostructures
• Origins of singlet fission in solid pentacene from an ab initio Green's-function approach
• Ultrafast Tracking of Exciton and Charge Carrier Transport in Optoelectronic Materials on the Nanometer Scale
• The impact of exciton delocalization on exciton-vibration interactions in organic semiconductors
• Resolving ultrafast exciton migration in organic solids at the nanoscale
• Strongly-bound excitons and trions in anisotropic 2D semiconductors

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• Chiral excitonics in monolayer semiconductors on patterned dielectric
• Electron energy-loss spectrum and exciton band structure of ${\mathrm{WSe}}_2$ monolayer studied by ab initio Bethe-Salpeter equation calculations
• Viscous hydrodynamics of excitons in van der Waals heterostructures
• Cross-dimensional valley excitons from Förster coupling in arbitrarily twisted stacks of monolayer semiconductors
• Dimensionality-Dependent Exciton Dispersion in a Single-Band Mott Insulator
• Chiral excitonic systems in twisted bilayers from Förster coupling and unconventional excitonic Hall effects
• \textit{Ab initio} \textit{GW}-BSE theory of optical activity in $\alpha$-quartz
• Phonon-assisted photoluminescence of bilayer MoS${}_2$ from first principles
• Strain-induced exciton mobility in layered WS2 from first principles