Pressure-induced superconductivity in the fcc phase of lithium: Strong-couplingapproach

The thermodynamic properties of the superconducting state in the fcc phase of lithium for the pressure (p) values 22.3 and 29.7 GPa have been determined by using the semi-phenomenological Eliashberg model. It has been shown, that the critical value of the Coulomb pseudopotential increases with p   from 0.22 to 0.36. The values of the dimensionless ratios 2Δ(0)/kBTC2Δ(0)/kBTC and ΔC(TC)/CN(TC)ΔC(TC)/CN(TC) are higher than in the BCS theory and grow together with p  . In contrast, the ratio TCCN(TC)/HC2(0) is smaller than in the BCS model and decreases with hydrostatic pressure's increasing. The Superconductors; Thermodynamic properties. numerical results have been supplemented by the analytical formula, which describes the dependence of the critical temperature on p in the considered pressure region.