The new metal–insulator transitions and nanoscale phase separation in doped cuprates

Dzhumanov, S.; Kurbanov, U.T.

doi:10.1016/j.spmi.2015.03.069

Cited by 3 publications

(3 citation statements)

References 28 publications

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“…We have demonstrated that the proposed two-carrier La-based cuprate superconductor model is more realistic than the previously studied single-carrier model of this superconductor, which was considered by many researchers (see Refs. [3,6,9,11,12,14]). This new model predicts much more reliable results for metal-insulator transitions in doped La-based cuprates than other existing results predicted by the single-carrier cuprate superconductor model.…”

Section: Discussionmentioning

confidence: 99%

“…where f I is the fraction of charge carriers residing in the impurity band, m I is the mass of such charge carriers, m p is the mass of large polarons, n is the concentration of doped charge carriers. In a two-carrier cuprate superconductor model, the conditions for carrier localization or the new criteria for metal-insulator transitions will be different from the criteria for metal-insulator transitions defined in the single-carrier cuprate superconductor model [14] and can be written as…”

Section: New Criteria For Metal-insulator Transitions Indoped La-base...mentioning

confidence: 99%

“…However, in these materials, doped charge carriers can reside near dopants (impurities) as bound carriers and in defect-free regions of the crystal lattice as polaronic carriers. Therefore, such two types of charge carriers can coexist in doped semiconductors and high-temperature cuprate superconductors, and the criterion for metal-insulator transition in the case of two coexisting charge carriers will differ from the criterion formetal-insulator transition obtained in the one-carrier semiconductor or high-T c superconductor model [14]. These circumstances were not previously considered in the studying metal-insulator transitions in doped materials.…”

Section: Introductionmentioning

confidence: 97%

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METAL-INSULATOR TRANSITIONS IN DOPED La-BASED SUPER CONDUCTORS WITH SMALL-RADIUS DOPANTS

Dzhumanov¹

2022

Eurasian phys. tech. j.

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n this work, we study the possibility of realizing two distinct mechanisms of metal-insulator transitions in hole-doped cuprates induced by the localization of charge carriers near the small-radius impurities and in a deformable lattice (i.e. in the absence of impurities). The purpose of this research is to determine the criteria (i.e. conditions) for the existence of the localized states of hole carriers and solve the problem of metal-insulator transitions in La-based cuprates. The advantage of La-based cuprate versus other types of cuprates is that two distinct metal-insulator transitions in La-based cuprates driven by the strong carrier-impurity-phonon and carrier-phonon interactions occur simultaneously in a wider doping range from the lightly doped to heavily doping regime. We show that at very low doping, the separate levels of hole carriers localized near impurities and in a deformable lattice are formed in the charge-transfer gap of the cuprates. As the doping level increases towards underdoped region, the energy levels of such charge carriers start to form energy bands which gradually broaden with increasing doping. We propose a new two-carrier cuprate superconductor model for studying two distinct metal-insulator transitions occurring simultaneouslyin hole-doped La-based cuprate compounds. We demonstrate that when hole carriers reside in impurity and polaron bands, these metal-insulator transitions in La-based superconductors with small-radius dopants occur accordingly in a wide doping range and relatively lower doping levels.

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Section: Discussionmentioning

confidence: 99%

Section: New Criteria For Metal-insulator Transitions Indoped La-base...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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METAL-INSULATOR TRANSITIONS IN DOPED La-BASED SUPER CONDUCTORS WITH SMALL-RADIUS DOPANTS

Dzhumanov¹

2022

Eurasian phys. tech. j.

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Metal-insulator transitions and magnetic susceptibility in doped cuprate compounds

Dzhumanov

Kurbanov

Khudayberdiev

et al. 2016

Low Temperature Physics

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Results are presented from a theoretical study of the possibility of hole carrier localization and metal-insulator transitions which show up in the temperature dependences of the magnetic susceptibility χ(T) of doped copper-oxide (cuprate) compounds. The criteria for metal-insulator transitions owing to strong hole-lattice interactions and the formation of very narrow polaron bands in these materials with reduced doping level x are analyzed. It is shown that these kinds of metal-insulator transitions occur in underdoped La2-xSrxCuO4 and YBa2Cu3O6+x cuprates (i.e., for x ranging from 0.04 to 0.12). The characteristic temperature dependences χ(T) of the HTSC cuprates are found for different doping levels. These results are in good agreement with experimental data on metal-insulator transitions and the magnetic susceptibility of the HTSC cuprates.

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Evolution of the pseudogap temperature dependence in YBa2Cu3O7–δ films under the influence of a magnetic field

Petrenko,

Rogacki,

Terekhov

et al. 2024

Low Temperature Physics

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The evolution of the temperature dependence of the pseudogap Δ*(T) in optimally doped (OD) YBa2Cu3O7–δ (YBCO) films with the superconducting critical temperature Tc = 88.7 K under the influence of a magnetic field B has been studied in detail. It has been established that the shape of Δ*(T) for various B over the entire range from the pseudogap opening temperature T* to T01, below which superconducting fluctuations occur, has a wide maximum at the BEC-BCS crossover temperature Tpair, which is typical for OD films and untwinned YBCO single crystals. T* was shown to be independent on B, whereas Tpair shifts to the low-temperature region along with the increase in B, while the maximum value of Δ*(Tpair) remains practically constant regardless of B. It was revealed that as the field increases, the low-temperature maximum near the 3D-2D transition temperature T0 is blurred and disappears at B > 5 T. Moreover, above the Ginzburg temperature TG, which limits superconducting fluctuations from below, for B > 0.5 T, a minimum appears on Δ*(T) at Tmin, which becomes very pronounced with a further increase in B. As a result, the overall value of Δ*(T) decreases noticeably most likely due to the pair-breaking effect. A comparison of Δ*(T) near Tc with the Peters–Bauer theory shows that the density of fluctuating Cooper pairs actually decreases from ⟨n↑n↓⟩ ≈ 0.31 at B = 0 to ⟨n↑n↓⟩ ≈ 0.28 in the field of 8 T. The observed behavior of Δ*(T) around Tmin is assumed to be due to the influence of a two-dimensional vortex lattice created by the magnetic field, which prevents the formation of fluctuating Cooper pairs near Tc.

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The new metal–insulator transitions and nanoscale phase separation in doped cuprates

Cited by 3 publications

References 28 publications

METAL-INSULATOR TRANSITIONS IN DOPED La-BASED SUPER CONDUCTORS WITH SMALL-RADIUS DOPANTS

METAL-INSULATOR TRANSITIONS IN DOPED La-BASED SUPER CONDUCTORS WITH SMALL-RADIUS DOPANTS

Metal-insulator transitions and magnetic susceptibility in doped cuprate compounds

Evolution of the pseudogap temperature dependence in YBa2Cu3O7–δ films under the influence of a magnetic field

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