Thermodynamics of the superconducting phase in compressed GeH4(H2)2

Recent studies on the hydrogen-rich metals are mainly stimulated by the fact that these superconductors are supposed to exhibit the high value of the critical temperature (T_C). The thermodynamic properties of GeH₄(H₂)₂ hydride under the pressure at 250 GPa have been studied in the present paper. The calculations have been conducted in the framework of the Eliashberg approach for the wide range of the Coulomb pseudopotential values: μ^⋆∈<0.1,0.3>. It has been found that the critical temperature is high in the entire range of the Coulomb pseudopotential: T_C∈<128.5,69.8> K. The values of the thermodynamic dimensionless ratios, namely R_Δ≡2Δ(0)/k_BT_C, R_C≡ΔC(T_C)/C^N(T_C), and R_H≡T_CC^N(T_C)/HC2(0), differ from the predictions of the Bardeen-Cooper-Schrieffer theory. In particular, R_Δ∈<4.30,4.08>, R_C∈<1.91,1.58>, and R_H∈<0.151,0.154>. Finally, the ratio of the electron effective mass (me⋆) to the electron band mass (m_e) reaches the maximum at the critical temperature, where me⋆/m_e=2.45.