Theory of excitonic polarons: From models to first-principles calculations

Abstract

Excitons are neutral excitations that are composed of electrons and holes bound together by their attractive Coulomb interaction. The electron and the hole forming the exciton also interact with the underlying atomic lattice, and this interaction can lead to a trapping potential that favors exciton localization. The quasi-particle thus formed by the exciton and the surrounding lattice distortion is called excitonic polaron. Excitonic polarons have long been thought to exist in a variety of materials, and are often invoked to explain the Stokes shift between the optical absorption edge and the photo-luminescence peak. However, quantitative ab initio calculations of these effects are exceedingly rare. In this manuscript, we present a theory of excitonic polarons that is amenable to first-principles calculations. We first apply this theory to model Hamiltonians for Wannier excitons experiencing Fröhlich or Holstein electron-phonon couplings. We find that, in the case of Fröhlich interactions, excitonic polarons only form when there is a significant difference between electron and hole effective masses. Then, we apply this theory to calculating excitonic polarons in lithium fluoride ab initio. The key advantage of the present approach is that it does not require supercells, therefore it can be used to study a variety of materials hosting either small or large excitonic polarons. This work constitutes the first step toward a complete ab initio many-body theory of excitonic polarons in real materials.

References in corpus (27)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Phonons and related properties of extended systems from density-functional perturbation theory
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Optimized norm-conserving Vanderbilt pseudopotentials
• The PseudoDojo: Training and grading a 85 element optimized norm-conserving pseudopotential table
• Wannier90 as a community code: new features and applications
• Electron-phonon interactions from first principles
• EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions
• Yambo: an \textit{ab initio} tool for excited state calculations
• BerkeleyGW: A Massively Parallel Computer Package for the Calculation of the Quasiparticle and Optical Properties of Materials and Nanostructures
• Many-body perturbation theory calculations using the yambo code
• Fröhlich electron-phonon vertex from first principles
• Polaron Problem by Diagrammatic Quantum Monte Carlo
• Nonanalyticity, Valley Quantum Phases, and Light-like Exciton Dispersion in Monolayer TMDs: Theory and First-Principles Calculations
• Efficient $\mathcal{O}(N^2)$ approach to solve the Bethe-Salpeter equation for excitonic bound states
• Exciton band structure in two-dimensional materials
• Ab initio theory of polarons: formalism and applications
• Polarons from first principles, without supercells
• Exciton-Phonon Interaction and Relaxation Times from First Principles
• Excited-state Forces within a First-principles Green's Function Formalism
• Polarons in two-dimensional atomic crystals
• Floquet engineering of strongly-driven excitons in monolayer tungsten disulfide
• Unified approach to polarons and phonon-induced band structure renormalization
• Large scale GW-BSE calculations with N3 scaling: excitonic effects in dye sensitised solar cells
• Excitonic polarons and self-trapped excitons from first-principles exciton-phonon couplings
• Ab initio self-consistent many-body theory of polarons at all couplings
• Unified ab initio description of Fröhlich electron-phonon interactions in two-dimensional and three-dimensional materials

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• The Wannier Function Software Ecosystem for Materials Simulations
• Identification of large polarons and exciton polarons in rutile and anatase polymorphs of titanium dioxide
• Polarons in the Cubic Generalized Fröhlich Model: Spontaneous Symmetry Breaking
• Polaron catastrophe within quantum acoustics
• How to choose efficiently the size of the Bethe-Salpeter Equation Hamiltonian for accurate exciton calculations on supercells
• Exciton pairs coupled via the long-living phonons and their superfluorescent markers