Vibronic Spectra of Molecular Crystals: Dynamic Theory and Comparison with Experiment

Rashba, Emmanuel I.

doi:10.1007/978-3-642-81482-2_6

Cited by 2 publications

(2 citation statements)

References 10 publications

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“…In 1957, Rashba and Davidov published an article in Ukrainian in the Ukrainian Physical Journal on optical absorption in a molecular crystal with a weak interaction between excitons and phonons [1]. Also in 1957, Rashba published a pair of articles in the Russian journal Optika i Spektroskopiya on the theory of electronic excitations interacting with lattice vibrations in a molecular crystal [2,3]. These articles considered cases of both light and heavy excitons, distinguishing excitons whose band width in the absence of lattice distortions is large or small on a scale depending on the strength of the particlephonon interactions, with particular attention to the case of strong interactions.…”

Section: Introductionmentioning

confidence: 99%

Low-energy tail of the spectral density for a particle interacting with a quantum phonon bath

Kim

Halperin

2023

Phys. Rev. B

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We describe two approximation methods designed to capture the leading behavior of the lowenergy tail of the momentum-dependent spectral density A(k, E) and the tunneling density of states D(E) for an injected particle, such as an electron or an exciton, interacting with a bath of phonons at a non-zero initial temperature T , including quantum corrections due to the non-zero frequencies of the relevant phonons. In our imaginary-time-dependent Hartree (ITDH) approximation, we consider a situation where the particle is injected into a specified coherent state of the phonon system, and we show how one can use the ITDH approximation to obtain the correlation function C(τ ) for that initial state. The thermal average C(τ ) is obtained, in principle, by integrating the result over all possible initial phonon coherent states, weighted by a thermal distribution. However, in the low-energy tail, one can obtain a good first approximation by considering only initial states near the one that maximizes the integrand. Our second approximation, the fixed-wave-function (FWF) approximation, assumes that the wave function of the injected particle evolves instantaneously to a wave function which then is independent of time, while the phonon system continues to evolve due to interaction with the particle. We discuss how to invert the Laplace transform and how to obtain A(k, E) as well as D(E) from the imaginary-time analysis. The FWF approximation is used to calculate D(E) for a one-dimensional continuum model of a particle interacting with acoustic phonons, and effects due to the quantum motion of phonons are observed. In the classical phonon limit, where the nuclear mass is taken to infinity while the elastic constants and other parameters are held fixed, the dominant behaviors of both the ITDH and FWF approximations in the low-energy tail reduce to that found in the past for a particle in a random potential with a Gaussian statistical distribution.

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Section: Introductionmentioning

confidence: 99%

Low-energy tail of the spectral density for a particle interacting with a quantum phonon bath

Kim

Halperin

2023

Phys. Rev. B

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“…Such kind of STE in binary mixed crystal is called extrinsic self-trapping. 27 The coexistence of STE and FE indicates a thermal activation barrier against self-trapping, 28 on either side of which the two distinguishable states lie on the minima of the adiabatic potential (Figure 2a). As the temperature-dependent PL shown in Figure 2b, the intensity of BE is considerable even at low temperature owing to the formation of STE from direct self-trapping and tunneling.…”

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Correlated Self-Trapped Excitons and Free Excitons with Intermediate Exciton–Phonon Coupling in 2D Mixed-Halide Perovskites

Yang,

Wei,

Gong

et al. 2023

J. Phys. Chem. Lett.

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Low-dimensional lead halides have attracted increasing attention due to their potential application as single-component white-light emitters. These materials exhibit a complex emission spectral structure, ranging from free exciton narrowband emissions to self-trapped exciton broadband emissions. However, there is still no consensus for the underlying physical mechanism, especially in the spectrum with both narrowband and broadband emissions. Here we aim to elucidate the correlation between the emission spectrum and the exciton–phonon coupling in the mixed halide perovskite BA2Pb(Br x Cl1–x )4. Our findings reveal that the interplay between exciton localization and delocalization results in an intermediate exciton–phonon coupling, leading to line shapes beyond the Huang–Rhys model for the self-trapped exciton. By incorporating the exciton motional effect, we establish a unified photophysical model describing the emission spectrum from the self-trapped exciton type to the free exciton type. These results provide essential insights into the mechanisms governing exciton–phonon interactions and offer ways to control white-light emission in two-dimensional perovskites.

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Vibronic Spectra of Molecular Crystals: Dynamic Theory and Comparison with Experiment

Cited by 2 publications

References 10 publications

Low-energy tail of the spectral density for a particle interacting with a quantum phonon bath

Low-energy tail of the spectral density for a particle interacting with a quantum phonon bath

Correlated Self-Trapped Excitons and Free Excitons with Intermediate Exciton–Phonon Coupling in 2D Mixed-Halide Perovskites

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