The investigation of the hydride superconductor's parabolic-like critical temperature under high pressure

Under the weak coupling, we investigate the critical temperatures under pressure of H3S, LaH10, CaH6, and Tl2Ba2CaCu2O8+{\delta} superconductors. The superconducting mechanism takes into account the electron-phonon interaction as well as the Coulomb interaction. Under high pressure, the critical temperature equation is calculated as a function of the fractional volume of the unit cell, and the Birch-Murnaghan equation of state is used to determine the relationship between fraction volume and pressure. Using this equation, we can analyze the parabolic-like relationship between the critical temperature and pressure of a superconductor. The parabolic behavior of these superconductors' critical temperature versus pressure can fit well. The maximal critical temperature of Tl2Ba2CaCu2O8+{\delta}, H3S, LaH10, and CaH6 superconductors are predicted to be 112 K at 7 GPa, 197 K at 140 GPa, 252 K at 143 GPa, and 207 K at 174 GPa, respectively.Comment: 14 pages, 4 Figure

Investigate the effect of anisotropic order parameter on the specific heat of anisotropic two-band superconductors

The effect of anisotropic order parameter to specific heat of anisotropic two-band superconductors in BCS weak-coupling limit are investigated. An analytical specific heat jump and the numerical specific heat are shown by using anisotropic order parameters, and the electron-phonon interaction and non-electron-phonon interaction. The two model of anisotropic order parameters are used for numerical calculation that we find little effect to the numerical results . The specific heat jump of, and superconductors can fit well with the both of them. By comparing to experimental data overall range of temperature, the best fit is ,, and superconductors, respectively.Comment: 10 pages, 3 fingure

Effect of density of state on isotope effect exponent of two-band superconductors

The exact formula of Tc's equation and the isotope effect exponent of two-band s-wave superconductors in weak-coupling limit are derived by considering the influence of two kinds of density of state : constant and van Hove singularity. The pairing interaction in each band consisted of 2 parts : the electron-phonon interaction and non-electron-phonon interaction are included in our model. We find that the interband interaction of electron-phonon show more effect on isotope exponent than the intraband interaction and the isotope effect exponent with constant density of state can fit to an experimental data,MgB2, and high-Tc superconductors, better than van Hove singularity density of state.Comment: 11 pages. accepted in Physica

Hc2 of anisotropy two-band superconductors by Ginzburg-Landau approach

The purpose of this research is to study the upper critical field (Hc2) of two-band superconductors by two-band Ginzburg - Landau approach. The analytical formula of Hc2 included anisotropy of order parameter and anisotropy of effective-mass are found . The parameters of the upper critical field in ab-plane and c-axis can be found by fitting to the experimental data . Finally, we can find the ratio of upper critical field that temperature dependent in the range of experimental result .Comment: 10 pages. accepted by Physica

EFFECT OF FLUORINE ON SOME PROPERTIES OF Y235 SUPERCONDUCTOR

The purpose of this research aims to study the physical properties of the Y123 and Y235 superconductor doped fluorine by solid state reaction.The conventional process with the calcination temperature at 810 °C and the sintering temperature at 925 °C were done. The samples obtained with optimal doping had the highest critical temperature at 95 K and 93 K for Y123 and Y235, respectively. There was no effect of doping on lattice parameters but the anisotropy parameter of Y235 was dependent on fluorine doping. The iodometric titration method was done that the pure Y123 and Y235 were shown the highest of Cu 3+ /Cu 2+ ratio and deficiency parameter. We also found the highest amount of Cu 3+ /Cu 2+ ratio at the optimal fluorine doping