Polaron crossover in molecular solids

Zoli, Marco; Das, Anindita

doi:10.1088/0953-8984/16/21/009

Cited by 18 publications

(16 citation statements)

References 46 publications

(58 reference statements)

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“…The third and fourth terms of Eq.1 represent the electron-phonon interaction and phonon harmonic energy, respectively. These terms may be written in the momentum space defined by the phonon creation operators: b † q = (1/ √ N ) i b † i e iq.R i and the corresponding annihilation operators, where N is the number of sites in the system 5,6,14 . It can be easily shown that the in-phase (q = 0) phonon mode does not couple with the electron dynamics but with the total number of electrons of the system.…”

Section: Formalismmentioning

confidence: 99%

Thermodynamic properties of Holstein polarons and the effects of disorder

Das¹,

Sil²

2008

J. Phys.: Condens. Matter

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The ground state and finite temperature properties of polarons are studied considering a two-site and a four-site Holstein model by exact diagonalization of the Hamiltonian. The kinetic energy, Drude weight, correlation functions involving charge and lattice deformations, and the specific heat have been evaluated as a function of electron-phonon (e-ph) coupling strength and temperature. The effects of site diagonal disorder on the above properties have been investigated. The disorder is found to suppress the kinetic energy and the Drude weight, reduces the spatial extension of the polaron, and makes the large-to-small polaron crossover smoother. Increasing temperature also plays similar role. For strong coupling the kinetic energy arises mainly from the incoherent hopping processes owing to the motion of electrons within the polaron and is almost independent of the disorder strength. From the coherent and incoherent contributions to the kinetic energy, the temperature above which the incoherent part dominates is determined as a function of e-ph coupling strength.

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Section: Formalismmentioning

confidence: 99%

Thermodynamic properties of Holstein polarons and the effects of disorder

Das¹,

Sil²

2008

J. Phys.: Condens. Matter

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“…This effect is more pronounced in higher dimensionality. 13 On the other hand, the dispersive nature of the phonon spectrum is recognized as a fundamental feature of the Holstein model as it allows for finite values of the electronic site jump probability while a dispersionless model would lead to un-physical divergences. 12,14 Also ground state properties such as electron bandwidth and effective mass are more properly evaluated versus dimensionality within a dispersive model.…”

Section: Introductionmentioning

confidence: 99%

Nonlocal electron-phonon correlations in a dispersive Holstein model

Zoli

2005

Phys. Rev. B

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Due to the dispersion of optical phonons, long range electron-phonon ͑e-ph͒ correlations renormalize downwards the coupling strength in the Holstein model. We evaluate the size of this effect both in a linear chain and in a square lattice for a time averaged e-ph potential, where the time variable is introduced according to the Matsubara formalism. Mapping the Holstein Hamiltonian onto the time scale we derive the perturbing source current which appears to be nontime retarded. This property permits to disentangle phonon and electron coordinates in the general path integral for an electron coupled to dispersive phonons. While the phonon paths can be integrated out analytically, the electron path integrations have to be done numerically. The equilibrium thermodynamic properties of the model are thus obtained as a function of the electron hopping value and of the phonon spectrum parameters. We derive the e-ph corrections to the phonon free energy and show that its temperature derivatives do not depend on the e-ph effective coupling, hence, the Holstein phonon heat capacity is strictly harmonic. A significant upturn in the low temperature total heat capacity over T ratio is attributed to the electron hopping which largely contributes to the action.

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“…For example, for λ = 1.1λ c the diagonal m d (k x = k y ) and transverse m t (k x = −k y ) masses for the local EPI are m d = 200 and m t = 88 whereas for nonlocal EPI the masses m d = 20 and m t = 10 are considerably lighter. Lighter mass for nonlocal EPI [98,195,[260][261][262][263][264][265] or dispersive phonons [266][267][268][269] was observed in many models.…”

Section: Nonlocal Epimentioning

confidence: 99%

Manifestations of the Electron-Phonon Coupling in the Spectroscopy of High-Temperature Superconductors

Mishchenko

2010

Advances in Condensed Matter Physics

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A review of experimental and theoretical results on the spectroscopy of high-temperature superconductors is presented. The models where hole doped into antiferromagnet interacts both with magnetic subsystem and with phonons are considered. Theoretical results of these models for phonon spectra, angle resolved photoemission spectra, and optical conductivity are presented. Comparison with experimental data gives evidence for the strong electron-phonon coupling in the undoped and weakly doped high-temperature superconductors. The strength of electron-phonon coupling decreases with doping though at the optimal doping the compounds are still in the intermediate coupling regime.

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Polaron crossover in molecular solids

Cited by 18 publications

References 46 publications

Thermodynamic properties of Holstein polarons and the effects of disorder

Thermodynamic properties of Holstein polarons and the effects of disorder

Nonlocal electron-phonon correlations in a dispersive Holstein model

Manifestations of the Electron-Phonon Coupling in the Spectroscopy of High-Temperature Superconductors

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