The High Pressure Superconductivity of CaLi2 Compound: The Thermodynamic Properties

Abstract

The thermodynamic properties of the superconducting state in CaLi2 at 60 GPa have been described in the paper. The numerical analysis has been carried out in the framework of the Eliashberg formalism. It has been shown that: (i) the critical value of the Coulomb pseudopotential is equal to 0.20, which corresponds to the value of 1795 meV for the Coulomb potential; (ii) the critical temperature (T C ) cannot be correctly calculated by using the Allen-Dynes (AD) formula; (iii) the dimensionless ratios: $T_{C}C^{N} (T_{C} )/H^{2}_{C} (0 )$ , (C S (T C )−C N (T C ))/C N (T C ) and 2Δ(0)/k B T C take the non-BCS values: 0.157, 1.78 and 3.85, respectively. The symbol C N represents the specific heat in the normal state, C S denotes the specific heat in the superconducting state, H C (0) is the thermodynamic critical field near the temperature of zero Kelvin, and Δ(0) is the order parameter; (iv) the ratio of the electron effective mass ( $m^{\star}_{e}$ ) to the electron band mass (m e ) assumes a high value, in the whole range of the temperature, where the superconducting state exists. The maximum of $m^{\star}_{e}/m_{e}$ is equal to 2.15 for T=T C .