Large copper isotope effect on the pseudogap in the high-temperature superconductor HoBa 2 Cu 4 O 8

Temprano, D. Rubio; Mesot, J.; Janssen, Stefan; Conder, K.; Fürrer, A.; Соколов, А. Е.; Trounov, V.; Казаков, С. М.; Karpiński, J.; Müller, K. A.

doi:10.1007/s100510170343

Cited by 45 publications

(51 citation statements)

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“…This view is essentially based on the absence of isotope effects seen in some experiments [7] and the apparent d-symmetry of the superconducting wavefunction. However, accumulating experimental evidence exists for electronlattice effects in high temperature superconductors [8,10,11], and theories based on electron-phonon interactions have also been proposed [2,3,4,5]. Here we follow the idea that both electronic correlations and electron phonon interactions are important [12] and study a model in which a Hubbard Hamiltonian is coupled to dispersive phonons.…”

Section: Introductionmentioning

confidence: 93%

Dynamical two electron states in a Hubbard-Davydov model

et al. 2004

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We study a model in which a Hubbard Hamiltonian is coupled to the dispersive phonons in a classical nonlinear lattice. Our calculations are restricted to the case where we have only two quasi-particles of opposite spins, and we investigate the dynamics when the second quasi-particle is added to a state corresponding to a minimal energy single quasi-particle state. Depending on the parameter values, we find a number of interesting regimes. In many of these, discrete breathers (DBs) play a prominent role with a localized lattice mode coupled to the quasiparticles. Simulations with a purely harmonic lattice show much weaker localization effects. Our results support the possibility that DBs are important in HTSC.

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Section: Introductionmentioning

confidence: 93%

Dynamical two electron states in a Hubbard-Davydov model

et al. 2004

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“…Nonetheless this constitutes a remarkably wide precursor superconductive behaviour, clearly in evidence in quantities like the diamagnetism [67], the paraconductivity [68] and the specific heat [23]. There are indications of the above developments too from the decrease in the current noise signal [69] and from modification to the rare-earth-based 4f crystal-field excitations in for example HoBa 2 Cu 4 O 8 [70]. The latter changes are the result of 4f coupling into the Cu 3d spin field and are recorded by means of inelastic neutron spin scattering.…”

Section: Brief Resumé Of the Chemical Negative-u Approach To Htscmentioning

confidence: 99%

Developments in the negative-Umodelling of the cuprate HTSC systems

Wilson

2001

J. Phys.: Condens. Matter

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This paper emphasizes once more the many strands which go into creating the unique and complex nature of the mixed-valent HTSC cuprates, above T c as below. Clearly it is not sensible to look in isolation to the lattice, magnetic or electronic aspects of the situation. Circumstances are too tightly coupled and interdependent. What one is in a position to do is to ascribe some preeminence in these matters. The line taken in this paper, as in its predecessors, is that charge constitutes the prime mover, but this taken within a chemical context, relating to bonding effects in the copper oxides and to a crucial shell-filling negative-U term of large magnitude. What dictates the uniqueness of copper in this is its particular position within the periodic table at the end of the 3dseries. This provides access to (i) three stable valencies, (ii) to the limited metallicity of tightbinding, mixed-valent YBa 2 Cu 3 O 7 , etc., (iii) to the p/d hybridized limitation of magnetic behaviour, and (iv) above all to the shell closure effects, with their dramatic energy adjustments of the relevant double-loading states when sited in high-valent local environment. This behaviour rests on the inhomogeneous electronic and structural conditions existing within these tight-binding mixed-valent systems. Normally such systems show strong positive-U behaviour and are magnetic. Here the shell-filling effects negate this U term to leave a net negative U eff of −3 eV per pair. That positions the bosonic electron pairs degenerate with E F . RVB spin coupling within the stripe phase geometry set up by the doped charge removes much spin-flip pair breaking, while the adopted 2D crystal structure with its saddle-point dominated F.S. provides the ideal k-space geometry from which to secure the negative-U driven pair formation. The Jahn-Teller effect associated with the d 9 electron count is crucial in upholding the two-subsystem nature of the HTSC materials.This paper looks at the support for this scenario that can be extracted from the recent work of Corson, Li, Mook, Valla, Norman, Varma, Gyorffy and many others. To the author it remains a mystery why other researchers have not examined the potential of this route for understanding the unique characteristics of the HTSC cuprates.3

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“…5 Many measurements have revealed the existence of complex superstructures and pseudogaps surrounding E F up to a temperature T ‫ء‬ , which is higher than T c in underdoped systems. Phonons are closely interacting with the electronic states, as shown by the softening of some phonon branches at certain dopings, [6][7][8] by isotope effects on T ‫ء‬ , on T c , 9 and on the width of the gap. 10 Stripelike regions with excitations of charge and spin modulations are seen in neutron-scattering experiments.…”

Section: Introductionmentioning

confidence: 99%

Spin-phonon coupling andq-dependence of spin excitations and high-Tcsuperconductivity from band models

Jarlborg

2009

Phys. Rev. B

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Spin-phonon coupling ͑SPC͒ has been shown to be compatible with many unusual properties of the high-T c copper oxides. Parameters from ab initio band calculations for unit cells of La 2 CuO 4 are used in a freeelectron-like model in order to study the variation in coupling between spin waves and different phonons. Different SPC for different phonons can explain the "hour-glass" shape of the spin excitations. The model predicts larger q vectors at less doping and rather complex isotope shifts. A link between the SPC parameters and the parameters for superconductivity is proposed. Also the pseudogap depends on the efficiency of SPC, and it will interfere with superconductivity at low doping. Different contributions to the coupling parameters are discussed. It is argued that SPC coming from the interaction between spin waves and O phonons can be strong enough to explain high T c .

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Large copper isotope effect on the pseudogap in the high-temperature superconductor HoBa 2 Cu 4 O 8

Cited by 45 publications

References 1 publication

Dynamical two electron states in a Hubbard-Davydov model

Dynamical two electron states in a Hubbard-Davydov model

Developments in the negative-Umodelling of the cuprate HTSC systems

Spin-phonon coupling andq-dependence of spin excitations and high-Tcsuperconductivity from band models

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