The Energy Gap in the (Hg1−x Sn x )Ba2Ca2Cu3O8+y Superconductor

Abstract

The experimental data show that the increase of tin in the (Hg 1−x Sn x )Ba 2 Ca 2 Cu 3 O 8+y superconductor results in a visible increase in the pseudogap temperature (T ) with a slight decrease in the value of the critical temperature (T C ). Based on the above results, the dependence of the average amplitude of the energy gap on the temperature (G(T )) has been determined for x ∈ 0, 0.25 . On this basis, it has been found that the dimensionless ratio R G ≡ G(0)/k B T C increases with the increasing tin content from the value of 3.48 to the value of 4.88. Next, for x = 0.25 and T ∈ 0, T , the dependence of the energy gap on the wave vector has been calculated in the surrounding of the Fermi level. It has been shown that in the anti-nodal region the energy gap is very weakly dependent on the temperature. On the other hand, in the nodal region its values strongly decrease together with the increasing temperature.Keywords High-T C superconductors · Thermodynamic properties · Electron-phonon couplingThe thermodynamic properties of the superconducting state in cuprates can be determined on the basis of two characteristic types of temperature: T C (the critical temperature) and T (the pseudogap temperature). The first temperature determines the disappearance of the superconducting state; the second one represents the value below which, in the normal state, the pseudogap appears in the electron density of states In the presented paper, the disorder induced by tin in the (Hg 1−x Sn x )Ba 2 Ca 2 Cu 3 O 8+y superconductor (Sndoped Hg-1223) has been considered. In particular, for the selected values of tin content, the dependence of the average amplitude of the energy gap on the temperature and the dependence of the energy gap on the wave vector have been calculated. The numerical analysis has been conducted in the framework of the recently introduced model [4,5].We notice that the model is based on the following postulates: The postulate (i) underlines the importance of the quasi two-dimensionality of the electron system. The second one draws attention to the electron-phonon pairing mechanism given by Fröhlich [6,7]. The third one postulates that the strong electron correlations in the cuprates are coupled with the phonon degrees of freedom. The first two postulates define the van Hove scenario [8][9][10][11][12]. The third postulate requires further discussion because it is far more subtle. In particular, it should be noted that the postulated electron correlations generalize the Hubbard approach [13]; the classical electron-electron interaction is replaced with the electronelectron-phonon coupling.

Description of High-Temperature Superconducting State in BSLCO Compound

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

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

“…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 .…”

High-pressure superconductivity in yttrium: The strong-coupling approach

“…Most researchers emphasize the importance of the strong electron correlations [9]. However, some of them pay attention to the role of the electron-phonon interaction [10][11][12][13][14][15].…”