Spectral properties and isotope effect in strongly interacting systems: Mott-Hubbard insulator versus polaronic semiconductor

Fratini, Simone; Ciuchi, S.

doi:10.1103/physrevb.72.235107

Cited by 28 publications

(32 citation statements)

References 47 publications

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“…Polaronic isotope effects in the spectral function of strongly correlated systems were numerically studied by (Fratini and Ciuchi , 2005) in the framework of the Holstein-Hubbard model and by (Mishchenko and Nagaosa, 2006) using the extended t − J model including EPI.…”

Section: Fröhlich Interaction)mentioning

confidence: 99%

Fröhlich polaron and bipolaron: recent developments

2009

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It is remarkable how the Fröhlich polaron, one of the simplest examples of a Quantum Field Theoretical problem, as it basically consists of a single fermion interacting with a scalar Bose field of ion displacements, has resisted full analytical or numerical solution at all coupling since ∼ 1950, when its Hamiltonian was first written. The field has been a testing ground for analytical, semi-analytical, and numerical techniques, such as path integrals, strong-coupling perturbation expansion, advanced variational, exact diagonalisation (ED), and quantum Monte Carlo (QMC) techniques. This article reviews recent developments in the field of continuum and discrete (lattice) Fröhlich (bi)polarons starting with the basics and covering a number of active directions of research. * Electronic address: jozef.devreese@ua.ac.be † Electronic address: a.s.alexandrov@lboro.ac.uk

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Section: Fröhlich Interaction)mentioning

confidence: 99%

Fröhlich polaron and bipolaron: recent developments

2009

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“…2(c) and 2(d), predicting a broader peak for 18 O. Second, models [32,33] incorporating interaction strength going beyond the Migal-Eliashberg theory were shown to be able to explain the large (small) isotope effect at high (low) energy and also the sharpening of ARPES peak induced by 18 O. On the other hand, the sign change of Figs.…”

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confidence: 92%

Strong and Complex Electron-Lattice Correlation in Optimally DopedBi2Sr2CaCu2O8+δ

Zhou²,

Mc³

et al. 2006

Phys. Rev. Lett.

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We discuss the nature of electron-lattice interaction in optimally doped Bi_{2}Sr_{2}CaCu_{2}O_{8+delta} samples, using the isotope effect (IE) in angle resolved photoemission spectroscopy (ARPES) data. The IE in the ARPES linewidth and the IE in the ARPES dispersion are both quite large, implying a strong electron-lattice correlation. The strength of the electron-lattice interaction is "intermediate," i.e., stronger than the Migdal-Eliashberg regime but weaker than the small polaron regime, requiring a more general picture of the ARPES kink than the commonly used Migdal-Eliashberg picture. The two IEs also imply a complex interaction, due to their strong momentum dependence and their differing sign behaviors. In sum, we propose an intermediate-strength coupling of electrons to localized lattice vibrations via charge density fluctuations.

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“…An effect which may also play a role is a ph-induced broadening of the higher-energy features in the spectrum which gets smaller upon decreasing ω ph , thus increasing the pseudogap. 43 Furthermore, our findings may be related to a recently proposed composite-fermion theory in which a reduction of the degree of coherence of quasiparticles due a smaller ω ph would lead to an increase of the "cofermion" binding energy and consequently of the pseudogap. 44 However, here we want to discuss the following very simple interpretation: Phonons mediate an attraction between electrons with a characteristic frequency scale set by ω ph .…”

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confidence: 75%

Isotope effect in the pseudogap state of high-temperature copper oxide superconductors

Sangiovanni

Gunnarsson

2011

Phys. Rev. B

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We study cuprates within the dynamical cluster approximation and find that the pseudogap displays an isotope effect of the same sign as observed experimentally. Notwithstanding the nonphononic origin of the pseudogap, the interplay between electronic repulsion and retarded phonon-mediated attraction gives rise to an isotope dependence of the antinodal spectra. Due to the strong momentum differentiation, such an interplay is highly nontrivial and leads to the simultaneous presence of heavier quasiparticles along the nodal direction. We predict an isotope effect in electron-doped materials.Copper-oxide superconductors are characterized by the highest superconducting transition temperatures ever measured and, 25 years after their discovery, the pairing mechanism, to the best of our knowledge, has not yet been clarified. However, this is probably not the main reason why these materials are so intriguing. Indeed, due to the complex interplay between their electronic, magnetic, and lattice degrees of freedom, we still have a very incomplete understanding even of their normal (nonsuperconducting) phase. The most well-known anomaly characterizing the cuprates at small values of doping is the presence of a pseudogap. Using the language of angular-resolved photoemission spectroscopy, the pseudogap is a strong suppression of the photoemission signal in selected parts of the Brillouin zone (BZ), occurring below a characteristic temperature called T * . This phenomenon is believed to be so relevant that any complete theory of cuprates should explain it.Differently from the superconducting transition temperature T c , T * displays a quite marked isotope effect characterized by a negative coefficient, i.e., it increases upon substituting oxygen or copper atoms with correspondingly heavier isotopes. 1-4 This represents an unusual dependence, having conventional BCS theory in mind. Some possible scenarios for its explanation have been proposed: Assuming that the pairing in cuprates is directly mediated by phonons 5 so that the pseudogap is associated to the binding of two polarons with no long-range phase coherence, Ranninger calculated the isotope shift of T * and found good qualitative agreement with experiments. The main drawback of this approach is that a small electronic repulsion is enough to make bipolaron formation energetically highly unfavorable, and in cuprates local Coulomb repulsion can by no means be neglected. Another theoretical prediction available is based on the idea of a quantum critical point at optimal doping: By analyzing the effects of critical fluctuations, Andergassen et al. proposed a consistent picture of the experimental observation. 6 Yet, to the best of our knowledge, no calculation has been done so far to see whether or not an isotope effect on T * is to be expected within probably the simplest model for cuprates, namely, a one-band tight-binding model for electrons or holes on the copper sites with nearest-neighbor and diagonal hopping t and t , respectively, experiencing a local Hubbard repulsion...

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Spectral properties and isotope effect in strongly interacting systems: Mott-Hubbard insulator versus polaronic semiconductor

Cited by 28 publications

References 47 publications

Fröhlich polaron and bipolaron: recent developments

Fröhlich polaron and bipolaron: recent developments

Strong and Complex Electron-Lattice Correlation in Optimally DopedBi2Sr2CaCu2O8+δ

Isotope effect in the pseudogap state of high-temperature copper oxide superconductors

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