Description of the thermodynamic properties of BiH5 and BiH6 superconductors beyond the mean-field approximation

• Published in: Solid state communications Vol. 279; pp. 27 - 29
• Main Authors: Jarosik, M.W., Drzazga, E.A., Domagalska, I.A., Szczȩśniak, K.M., Stȩpień, U.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2018
• Subjects: Electron-phonon superconductivity; Eliashberg theory; High-pressure effect; Hydrogen-rich materials; Thermodynamic properties; Hydrogen-rich materials; High-pressure effect; Thermodynamic properties; Eliashberg theory; Electron-phonon superconductivity
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2018.05.009

The ab initio calculations suggest (Y. Ma et al.), that the high-pressure (p = 200 GPa) superconducting state in BiH5 and BiH6 compounds characterizes with a high value of the critical temperature (TC ∼ 100 K). Due to the large value of the electron-phonon coupling constant (λ ∼ 1.2), the thermodynamic parameters of the superconducting phase in BiH5 and BiH6 have been determined beyond the mean-field approximation - in the framework of the Eliashberg equations formalism. We have calculated the dependence of the order parameter (Δ) and the wave function renormalization factor on the temperature. Then we have estimated the free energy difference between the superconducting state and the normal state, the thermodynamic critical field (HC) and the specific heat of the superconducting state (CS) and the normal state (CN). The values of the dimensionless ratios RΔ=2Δ0/kBTC, RC=ΔCTC/CNTC and RH=TCCNTC/HC20 are equal RΔBiH5=4.17 and RΔBiH6=4.20, RCBiH5=2.54 and RCBiH6=2.58, RHBiH5=0.146 and RHBiH6=0.146 respectively.
•Hydrogen-rich materials.•High-pressure effect.•Electron-phonon superconductivity.•Eliashberg theory.•Thermodynamic properties.