Underlying mechanisms of pseudogap phenomena and Bose-liquid superconductivity in high- T c cuprates

Dzhumanov, S.; Karimboev, E.X.; Djumanov, Sh.S.

doi:10.1016/j.physleta.2016.04.038

Cited by 27 publications

(21 citation statements)

References 49 publications

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“…In our opinion such state can be interpreted as state with a pseudogap. However this state principally differs from the models of pseudogap in high-T c superconductors [10,[19][20][21][22], where preformed uncorrelated pairs are formed due to strong electron-electron interaction, but the phase coherence is possible only at more low temperature or at more large concentration of the pairs. In our model the uncorrelated pairs are pairs in momentum space (unlike bipolarons which are pairs in real space) which exist in noninteracting Fermi system due to the external pair potential.…”

Section: The Modelmentioning

confidence: 79%

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BCS theory with the external pair potential

Grigorishin

2017

Physics Letters A

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-b Metrolohichna str. Kiev-03680, Ukraine.We consider a hypothetical substance, where interaction between (within) structural elements of condensed matter (molecules, nanoparticles, clusters, layers, wires etc.) depends on state of Cooper pairs: an additional work must be made against this interaction to break a pair. Such a system can be described by BCS Hamiltonian with the external pair potential term. In this model the potential essentially renormalizes the order parameter: if the pairing lowers energy of the structure the energy gap is slightly enlarged at zero temperature and asymptotically tends to zero as temperature rises. Thus the critical temperature of such a superconductor is equal to infinity formally. For this case the effective Ginzburg-Landau theory is formulated, where the coherence length decreases as temperature rises, the GL parameter and the second critical field are increasing functions of temperature unlike the standard theory. If the pairing enlarges energy of the structure then suppression of superconductivity and the first order phase transition occur.

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Section: The Modelmentioning

confidence: 79%

“…Apparently the gap ∆ T cannot be order parameter, but it can mean presence of uncorrelated pairs. In its turn the systems with "preformed" Cooper pairs have been considered in works [9][10][11]. In this regime, the electrons are paired, but they lack the phase coherence necessary for superconductivity.…”

Section: Introductionmentioning

confidence: 99%

BCS theory with the external pair potential

Grigorishin

2017

Physics Letters A

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“…It should be noted that the local pair is not a local boson. Following [37] if the size of a local pair a p is much larger than the mean distance R p between the pairs then the bosonization of such local pairs cannot be realized due to their strong overlapping. Thus for fermionic nature of the pair it should be a p /R p > 1.…”

Section: Local Pairingmentioning

confidence: 99%

The role of electron–vibron interaction and local pairing in conductivity and superconductivity of alkali-doped fullerides

Grigorishin

2019

Physica C: Superconductivity and its Applications

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b Metrolohichna str. Kiev-03680, Ukraine.We investigate the competition between the electron-vibron interaction (interaction with the Jahn-Teller phonons) and the Coulomb repulsion in a system with the local pairing of electrons on the 3-fold degenerate lowest unoccupied molecular orbital (LUMO). The el.-vib. interaction and the local pairing radically change conductivity and magnetic properties of alkali-doped fullerides AnC60, which would have to be antiferromagnetic Mott insulators: we have shown that materials with n = 1, 5 and A = K, Rb are conductors but not superconductors; n = 3 and A = K, Rb are conductors and superconductors at low temperatures, but with A = Cs they are Mott-Jahn-Teller insulators at normal pressure; n = 2, 4 are nonmagnetic Mott insulators. Thus superconductivity, conductivity and insulation of these materials have common nature. Using this approach we obtain the phase diagram of A3C60 analytically, which is the result of interplay between the local pairing, the el.-vib. interaction, Coulomb correlations, and formation of small radius polarons.

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“…It was argued [70] that the Cooper pairing without superconductivity may occur at low carrier concentrations in semiconductors. Similarly, the Cooper pairing of polarons at a characteristic temperature * above c may occur in a degenerate polaronic Fermi gas with F ≫ B , namely, in sufficiently broadened polaronic band [71], while the charge carriers in the narrow impurity band (i.e., charge carriers trapped by impurities) remain unpaired [72]. One can expect that the BCS-type Cooper pairing of large polarons occurs without superconductivity above c in carrier-rich regions of underdoped cuprates, while the real-space pairing of such polarons in carrier-poor regions leads to the formation of large bipolarons.…”

Section: Temperature Dependence Of the Magnetic Susceptibility In Undmentioning

confidence: 99%

Distinctive Features of Metal-Insulator Transitions, Multiscale Phase Separation, and Related Effects in Hole-Doped Cuprates

Dzhumanov¹,

Khidirov²,

Kurbanov³

et al. 2019

Ukr. J. Phys.

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We study the distinctive features of the metal-insulator transitions, multiscale phase separation, and evolution of coexisting insulating and metallic/superconducting phases in hole-doped cuprates. We show how these interrelated phenomena and related effects manifest themselves in a wide doping range from the lightly doped to optimally doped regime in these systems, where the localized and mobile hole carriers reside in hole-poor (insulating) and hole-rich (metallic or superconducting) regions. We argue that small hole-rich regions (i.e. narrow nanoscale metallic islands or stripes) can persist in the insulating phase of the lightly doped cuprates, while the competing insulating, metallic, and superconducting phases would coexist in the under-doped cuprates. When the doping level is increased further, the hole-poor regions (or insulating zones) gradually narrow from macroscale to nanoscale insulating stripes and disappear in the optimally doped cuprates. We demonstrate clearly that the metal-insulator transitions and the coexisting insulating and metallic/superconducting phases are manifested in the suppression of superconductivity in underdoped cuprates and in the different temperature-dependent behaviors of the magnetic susceptibility and c-axis resistivity of lightly to optimally doped cuprates.

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Underlying mechanisms of pseudogap phenomena and Bose-liquid superconductivity in high- T c cuprates

Cited by 27 publications

References 49 publications

BCS theory with the external pair potential

BCS theory with the external pair potential

The role of electron–vibron interaction and local pairing in conductivity and superconductivity of alkali-doped fullerides

Distinctive Features of Metal-Insulator Transitions, Multiscale Phase Separation, and Related Effects in Hole-Doped Cuprates

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