Superconductivity in CuIr2-x Al x Te4 telluride chalcogenides

The relationship between charge-density-wave (CDW) and superconductivity (SC), two vital physical phases in condensed matter physics, has always been the focus of scientists' research over the past decades. Motivated by this research hotspot, we systematically studied the physical properties of the layered telluride chalcogenide superconductors CuIr2-x Al x Te4 (0 ≤ x ≤ 0.2). Through the resistance and magnetization measurements, we found that the CDW order was destroyed by a small amount of Al doping. Meanwhile, the superconducting transition temperature (T c ) kept changing with the change of doping amount and rose towards the maximum value of 2.75 K when x = 0.075. The value of normalized specific heat jump (ΔC/γT c ) for the highest T c sample CuIr1.925Al0.075Te4 was 1.53, which was larger than the BCS value of 1.43 and showed that bulk superconducting nature. In order to clearly show the relationship between SC and CDW states, we propose a phase diagram of T c vs. doping content.

Specific Heat Investigation in Iron-Based Superconductors

We have proposed a mean field theoretical model in the coexistence of superconductivity and Jahn–Teller (JT) effect for the study of specific heat in iron-based superconductors in the presence of an external magnetic field. The superconducting (SC) gap and lattice strain energy expressions are calculated using Zubarev’s technique of double-time electron Green’s function and solved numerically. The specific heat jump at the critical temperatures are observed. Keeping fixed the SC transition temperature at 28[Formula: see text]K for the iron pnictide [Formula: see text] like superconductors, the coefficient of electronic specific heat [Formula: see text] at low temperatures is determined to be 5.75[Formula: see text]mJ/mol[Formula: see text]K2 in the pure SC state and 4.76[Formula: see text]mJ/mol[Formula: see text]K2 in the coexistence state of SC and JT effect which are in agreement with some experimental results. The effect of the external magnetic field on the specific heat is studied.

Effect of pseudogap on the specific heat of superconductor

In this paper, the superconductor with the competition of superconducting gap and pseudogap in the below crossover temperature region is calculated. The superconducting gap and pseudogap is assumed to arise from independent and competing correlation. The critical temperature, superconducting gap and the specific heat jump are derived in the analytic form and the approximation is used to simplify the equations obtained for the region that crossover temperature and energy of pseudogap are higher than critical temperature. We find that the critical temperature is decreased as the energy of pseudogap and crossover temperature as increased. The superconductor with pseudogap has small specific heat jump in comparison with the BCS value. Increasing the crossover temperature and critical temperature, the specific heat jump is decreased.

Specific heat jump of two-band superconductor KFe2As2 using Ginzburg-Landau theory

In this study specific heat jump using two-gap Ginzburg-Landau (GL) theory has been calculated. In contrast to the previous approaches, we have taken into account intergradient order parameters interaction in the GL free energy functional. The thermodynamic magnetic field revealed nonlinear temperature dependence due to interband interaction between order parameters and their gradients. The calculations showed that the specific heat jump in two-order parameter superconductors was smaller than that of single-order parameter superconductors. It has been shown that such a model is in good agreement with experimental data for KFe2As2 superconductors.

Estimation of the superconducting parameters for silane at high pressure

The properties of the superconducting state in the Cmca phase of silane ( SiH4 ) at the pressure of 250 GPa have been considered. In particular, the critical temperature (TC), the free energy difference between the superconducting and normal state (ΔF ≡ FS - FN), the thermodynamic critical field (HC) and the specific heat jump (ΔC ≡ CS - CN) have been determined. It has been shown that the dimensionless ratios: [Formula: see text] and RC ≡ ΔC(TC)/CN(TC) assume the values: RH(μ⋆) ∈ 〈0.147, 0.154〉 and RC(μ⋆) ∈ 〈2.20, 1.79〉, where the symbol μ⋆ denotes the Coulomb pseudopotential and μ⋆∈ 〈0.1, 0.3〉.

The Specific Heat Jump of Hybridized Two-Band Superconductor

The specific heat jump of the two-band hybridized superconductor was studied. The two-band model is consist of conduction electron band and other-electron band with the upper and lower band of quasi-particle energy spectra occurred by hybridization. The specific heat jump was determined by making the assumption that the conduction electron band having the same energy as other-electron band, and the other-electron band having the energy near the Fermi energy. The analytic formula of specific heat jump of the two-band hybridized superconductor was derived and the effect of hybridization coefficient on the specific heat jump was investigated.