### Abstract

The thermodynamic parameters of the superconducting state in calcium under the pressure of 161GPa have been calculated within the framework of the Eliashberg approach. It has been shown that the value of the Coulomb pseudopotential is high (μ^{*} _{C}=0.24) and the critical temperature (T_{C}=25K) should be determined from the modified Allen-Dynes formula. In addition, it has been found that the basic dimensionless ratios of the thermodynamic parameters significantly diverge from the BCS predictions, and take the following values: (i) The zero-temperature energy gap to the critical temperature (R_{1}≡ 2Δ(0)/k_{B}T_{C}) is equal to 4.01. (ii) The ratio R_{2}≡ (C^{S}(T_{C}) equals 2.17, where C^{S}and C^{N}denote the specific heats for the superconducting and normal states, respectively. (iii) The quantity R_{3}≡T_{C}C^{N}(T_{C})/H^{2} _{C}(0)=0.158, where H_{C}indicates the thermodynamic critical field. Finally, it has been proven that the electron effective mass is large and takes the maximum of 2.32m_{e}at T_{C}.

Original language | English |
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Pages (from-to) | 2194-2201 |

Number of pages | 8 |

Journal | Physica Status Solidi (B) Basic Research |

Volume | 249 |

Issue number | 11 |

DOIs | |

Publication status | Published - Nov 2012 |

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### Keywords

- Ca Pnma phase
- High-pressure effects
- Superconductivity
- Thermodynamic properties

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics

### Cite this

*Physica Status Solidi (B) Basic Research*,

*249*(11), 2194-2201. https://doi.org/10.1002/pssb.201248032