The characterization of high-pressure superconducting state in compound: The strong-coupling description

Szczȩśniak, R.; Durajski, A. P.

doi:10.1016/j.jpcs.2012.12.024

Cited by 20 publications

(12 citation statements)

References 49 publications

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“…The numerical procedures discussed and tested in the works have been applied (see [19][20][21][22][23]). Figure 4 presents the full dependence of the energy gap on the angle α, where α ≡ arctan(k y /k x ).…”

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confidence: 99%

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

Szczȩśniak

Durajski

2014

J Supercond Nov Magn

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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.

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confidence: 99%

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

Szczȩśniak

Durajski

2014

J Supercond Nov Magn

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“…This interest stems from the fact that, in hydrides, it is theoretically possible to obtain a high critical temperature (T c ) at the pressure (p) which is much lower than the metallization pressure (∼ 400 GPa) for the pure metallic hydrogen [3,4]. In certain cases, like for example in the case of Si 2 H 6 , the critical temperature is expected, on the basis of the theoretical calculations [5], to be as high as 173 K at p = 275 GPa. Please note that this value of T C is even higher than for the cuprate superconductor HgBa 2 Ca 2 Cu 3 O 8+y , where the maximal critical temperature is equal to 164 K at p = 31 GPa [6].…”

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Thermodynamic Critical Magnetic Field for Chlorine Halide Superconductor at High Pressure

Szczęśniak¹,

Szczȩśniak

2014

Acta Phys. Pol. A

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At present, hydrides are considered as a one of the most interesting high-temperature superconductors with the classical electron-phonon pairing mechanism. In the present paper, we have analyzed the dependence of the thermodynamic critical magnetic eld (Hc) on the temperature for the chlorine halide superconductor. The calculations have been made in the framework of the Eliashberg formalism for the following pressure values: p1 = 320 GPa and p2 = 360 GPa. We have shown that Hc increases strongly with the increase of the pressure: [Hc (0) In recent years, hydrides have gained much attention as possible pressure-induced high-temperature superconductors with the conventional electron-phonon pairing mechanism [1,2]. This interest stems from the fact that, in hydrides, it is theoretically possible to obtain a high critical temperature (T c ) at the pressure (p) which is much lower than the metallization pressure (∼ 400 GPa) for the pure metallic hydrogen [3,4]. In certain cases, like for example in the case of Si 2 H 6 , the critical temperature is expected, on the basis of the theoretical calculations [5], to be as high as 173 K at p = 275 GPa. Please note that this value of T C is even higher than for the cuprate superconductor HgBa 2 Ca 2 Cu 3 O 8+y , where the maximal critical temperature is equal to 164 K at p = 31 GPa [6]. Thus, it is important to examine the promising superconducting properties of such hydrogen compounds.In the presented work, we have studied the dependence of the thermodynamic critical magnetic eld (H C ) on the temperature for the chlorine halide (HCl) superconductor. Despite of the fact that HCl contains a smaller number of the H atoms than the hydrogen-rich materials, the hitherto determined superconducting properties of this material are promising [7].The analysis of the HCl compound (within the P 2 1 /m crystal structure) has been carried out for the pressure values p 1 = 320 GPa and p 2 = 360 GPa. In the considered cases, the electron-phonon coupling constants In the paper, we have assumed that the electronphonon interaction is modeled by the Eliashberg functions originally calculated in [7], whereas the Coulomb pseudopotential (µ ) takes a typical value of 0.1.The critical magnetic eld at a given temperature can be calculated by using the expression (the CGS unit system) [9]:where ρ(0) stands for the value of the electron density of states at the Fermi level, and ∆F denotes the free energy dierence between the normal and the superconducting state. The latter one can be calculated as follows: The order parameter and the renormalization functions have been determined by solving the imaginary axis Eliashberg equations [9]. These complicated calculations have been made by using the iterative methods presented in the papers [10] and [11]. In the considered case, we have assumed that M = 1100, in order to ensure the stability of the numerical solutions for T ≥ T 0 ≡ 5 K.In the bottom panel of Fig. 1, we have presented the dependence of ∆F/ρ(0) on the temperature for the (344)

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“…In most of various approaches used to explain different properties of superconductors of the new generation, including those with high critical temperatures 46 , a single microscopic mechanism responsible for high- T c superconductivity is assumed. However, such mechanism has not been equivocally identified yet.…”

Section: Formalismmentioning

confidence: 99%

Simple analytical model of the effect of high pressure on the critical temperature and other thermodynamic properties of superconductors

Krzyzosiak

Gonczarek

et al. 2018

Sci Rep

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Within the general conformal transformation method a simplified analytical model is proposed to study the effect of external hydrostatic pressure on low- and high-temperature superconducting systems. A single fluctuation in the density of states, placed away from the Fermi level, as well as external pressure are included in the model to derive equations for the superconducting gap, free energy difference, and specific heat difference. The zero- and sub-critical temperature limits are discussed by the method of successive approximations. The critical temperature is found as a function of high external pressure. It is shown that there are four universal types of the response of the system, in terms of dependence of the critical temperature on increasing external pressure. Some effects, which should be possible to be observed experimentally in s-wave superconductors, the cuprates (i.e. high-Tc superconductors) and other superconducting materials of the new generation such as two-gap superconductors, are revealed and discussed. An equation for the ratio ≡ 2Δ(0)/Tc, as a function of the introduced parameters, is derived and solved numerically. Analysis of other thermodynamic quantities and the characteristic ratio ≡ ΔC(Tc)/CN(Tc) is performed numerically, and mutual relations between the discussed quantities are investigated. The simple analytical model presented in the paper may turn out to be helpful in searching for novel superconducting components with higher critical temperatures induced by pressure effects.

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The characterization of high-pressure superconducting state in compound: The strong-coupling description

Cited by 20 publications

References 49 publications

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

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

Thermodynamic Critical Magnetic Field for Chlorine Halide Superconductor at High Pressure

Simple analytical model of the effect of high pressure on the critical temperature and other thermodynamic properties of superconductors

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