Electron–Phonon Interaction in Mixed Valence Systems

Brouers, F.; Menezes, O.L.T. de

doi:10.1002/pssb.2221040218

Cited by 15 publications

(4 citation statements)

References 8 publications

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“…However, according to our results any infinitesimal hybridization, induced by some additional mechanism, could lead to a robust excitonic average due to the interband Coulomb interaction. Such an additional mechanism could be, for example, the electron-phonon interaction H el-ph that can be reduced to the phonon-mediated local hybridization (electron-electron interactions) by the standard canonical transformation of the form e S He −S , where the operator S is determined such that H el-ph = −[S, H loc ] and H loc are all local terms corresponding to f, d electrons and phonons [21].…”

Section: Resultsmentioning

confidence: 99%

“…In particular, we will show that the strong interband Coulomb interaction between the d and f electrons is able to enhance the excitonic d † f expectation value by a factor 100 and more in comparison to the noninteracting case, which is considerably more than predicted within the Hartree-Fock approximation with the CDW instability [20]. The effect is especially strong for V → 0, which indicates the possibility of stabilization of the EI phase in the strongly correlated systems by the presence of infinitesimal hybridization induced by some additional mechanisms like the electron-phonon interaction [21].…”

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confidence: 81%

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The influence of the interband Coulomb interaction and the f-electron hopping on excitonic correlations in the extended Falicov-Kimball model

Farkašovský¹

2015

EPL

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The density matrix renormalization group (DMRG) method is used to examine the effects of the interband Coulomb interaction U between f and d electrons as well as the f -electron hopping on the stability of the excitonic phase in the one-dimensional Falicov-Kimball model (FKM) with local hybridization V . It is found that the interband Coulomb interaction significantly enhances the excitonic P df = d + f average and that this effect is especially strong in the limit of small hybridization, where the interacting P df (U ) excitonic value is enhanced several hundred times in comparison to its non-interacting P df (U = 0) value. The further increase in P df is observed due to the non-zero f -electron hopping, but these changes are considerable only if the d and f bands have opposite parity. In addition, the examination of the interplay between the excitonic effects and the charge density wave (CDW) instability showed that the CDW and excitonic phase coexist up to relatively large values of local hybridization (V ∼ 0.13). The ground-state phase diagram of the model in the V -U plane is discussed.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 81%

The influence of the interband Coulomb interaction and the f-electron hopping on excitonic correlations in the extended Falicov-Kimball model

Farkašovský¹

2015

EPL

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“…However, according to our results, any infinitesimal hybridization, induced by some additional mechanism, could lead to a robust excitonic average due to the interband Coulomb interaction. Such an additional mechanism could be, for example, the electron-phonon interaction H el-ph that can be reduced to the phonon-mediated local hybridization (electron-electron interactions) by the standard canonical transformation of the form e S He −S , where the operator S is determined so that H el-ph = −[S, H loc ] and H loc are all local terms corresponding to f , d electrons and phonons [41].…”

Section: Effects Of Interband Coulomb Interactionmentioning

confidence: 99%

DMRG study of exciton condensation in the extended Falicov-Kimball model

Farkašovský¹

2020

Condens. Matter Phys.

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The formation and condensation of excitonic bound states of conduction-band electrons and valence-band holes surely belongs to one of the most exciting ideas of contemporary solid state physics. In this short review we present the latest progress in this field reached by the density-matrix-renormalization-group (DMRG) calculations within various extensions of the Falicov-Kimball model. Particular attention is paid to a description of crucial mechanisms (interactions) that affect the stability of the excitonic phase, and namely: (i) the interband 𝑑-𝑓 Coulomb interaction, (ii) the 𝑓 -electron hopping, (iii) the nonlocal hybridization with odd and even parity, (iv) combined effects of the local and nonlocal hybridization, (v) the nearest-neighbor Coulomb interaction between 𝑑 and 𝑓 electrons and (vi) the correlated hopping. The relevance of numerical results obtained within different extensions of the Falicov-Kimball model for a description of the real 𝑑-𝑓 materials is widely discussed.

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“…As shown by Menezes at al. [23] such an interaction can be reduced to the phonon-mediated local hybridization that can also lead to the formation of Bose-Einstein condensate under the supposition that it will be sufficiently strong, what depends on values of electron-phonon constants.…”

Section: Introductionmentioning

confidence: 99%

Formation and condensation of excitonic bound states in the generalized Falicov-Kimball model

Farkašovský

2017

Phys. Rev. B

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The density-matrix-renormalization-group (DMRG) method and the Hartree-Fock (HF) approximation with the charge-density-wave (CDW) instability are used to study a formation and condensation of excitonic bound states in the generalized Falicov-Kimball model. In particular, we examine effects of various factors, like the f -electron hopping, the local and nonlocal hybridization, as well as the increasing dimension of the system on the excitonic momentum distribution N (q) and especially on the number of zero momentum excitons N 0 = N (q = 0) in the condensate. It is found that the negative values of the f -electron hopping integrals t f support the formation of zero-momentum condensate, while the positive values of t f have the fully opposite effect. The opposite effects on the formation of condensate exhibit also the local and nonlocal hybridization. The first one strongly supports the formation of condensate, while the second one destroys it completely. Moreover, it was shown that the zero-momentum condensate remains robust with increasing dimension of the system.

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Electron–Phonon Interaction in Mixed Valence Systems

Cited by 15 publications

References 8 publications

The influence of the interband Coulomb interaction and the f-electron hopping on excitonic correlations in the extended Falicov-Kimball model

The influence of the interband Coulomb interaction and the f-electron hopping on excitonic correlations in the extended Falicov-Kimball model

DMRG study of exciton condensation in the extended Falicov-Kimball model

Formation and condensation of excitonic bound states in the generalized Falicov-Kimball model

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