On the Ratio of the Energy Gap Amplitude to the Critical Temperature for Cuprates

In the study, we have calculated the dependence of the average value of the energy gap amplitude (G) on the hole concentration (p) and temperature (T ) for the Bi 2 Sr 2−x La x CuO 6+δ (BSLCO) superconductor. The ratio of the zero temperature energy gap to the critical temperature (R G ≡ G (0) /k B T C ) and the ratio of the energy gap to the pseudogap temperature (R G ≡ G (0) /k B T ) have been estimated on this basis. It has been found that the value of the parameter R G changes for p ∈ 0.127, 0.198 in the range from 32.98 to 7.98. On the other hand, R G takes the values from 2.60 to 3.28. The obtained results indicate that in the studied superconductor, the correlation exists only between the value of the energy gap and the pseudogap temperature, which stands in the sharp contrast with the predictions of the classical Bardeen-Cooper-Schrieffer (BCS) theory. In addition, the dependence of the energy gap on the momentum for the hole concentration corresponding to the maximum value of the pseudogap temperature and the maximum value of the critical temperature has been determined. It has been found that the theoretical results reproduce well the experimental data obtained by using the angle-resolved photoemission spectroscopy (ARPES) method.

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“…At the same time, the determined values of the parameter R G fairly agree with the experimental results [1,13,14].…”

Section: The First Postulate States: In the Superconductivity Domain supporting

confidence: 85%

Description of High-Temperature Superconducting State in BSLCO Compound

Szczȩśniak

Durajski

2014

J Supercond Nov Magn

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“…In particular, it was shown that the model allows to calculate correctly the critical temperature and the energy gap at zero Kelvin. It should be noted that the appropriate calculations were carried out for the large number of the chemical compounds, and each time obtained results were consistent with the experimental data .…”

Section: The Eliashberg Approach the Pseudogap And The Pairing Mechsupporting

confidence: 62%

Pseudogap in the Eliashberg approach based on electron‐phonon and electron‐electron‐phonon interaction

2017

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The properties of the superconducting and the anomalous normal state were described by using the Eliashberg method. The pairing mechanism was reproduced with the help of the Hamiltonian, which models the electron-phonon and the electron-electron-phonon interaction (EEPh). The set of the Eliashberg equations, which determines the order parameter function (ϕ), the wave function renormalization factor (Z), and the energy shift function (χ ), was derived. It was proven that for the sufficiently large values of the EEPh potential, the doping dependence of the order parameter (ϕ/Z) has the analogous course to that observed experimentally in cuprates. The energy gap in the electron density of states is induced by Z and χ -the contribution from ϕ is negligible. The electron density of states possesses the characteristic asymmetric form and the pseudogap is observed above the critical temperature.

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“…For example, there are great difficulties in explaining the energy gap dependence on the temperature for the lower values of δ [39,[47][48][49][50]. The issue, which is not settled, is also the origin of the pseudogap.…”

Section: Introductionmentioning

confidence: 99%

Non-BCS Temperature Dependence of Energy Gap in Thin Film Electron-Doped Cuprates

Szczȩśniak

Durajski

2016

J Supercond Nov Magn

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We investigate the dependence of the energy gap (G) on the temperature (T ) for the electron-doped hightemperature superconductors. The following compounds, in the form of the thin films, have been taken into consideration: La 2−x Ce x CuO 4 (LCCO), Pr 2−x Ce x CuO 4 (PCCO), and Nd 2−x Ce x CuO 4 (NCCO). It was found that G(T ) deviates from the BCS prediction more, if a concentration of cerium assumes the lower values. For the lowest concentration (in the case of LCCO and NCCO), the function G (T ) is not quite like the BCS curve, which is connected with the existence of the residual Nernst region. Next, it has been pointed out that the NCCO superconductor becomes structurally unstable for the maximum concentration of cerium, which is leading to the anomalous dependence of the energy gap on the temperature and the induction of the wide Nernst region.

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On the Ratio of the Energy Gap Amplitude to the Critical Temperature for Cuprates

Cited by 8 publications

References 63 publications

Description of High-Temperature Superconducting State in BSLCO Compound

Description of High-Temperature Superconducting State in BSLCO Compound

Pseudogap in the Eliashberg approach based on electron‐phonon and electron‐electron‐phonon interaction

Non-BCS Temperature Dependence of Energy Gap in Thin Film Electron-Doped Cuprates

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