SPECIFIC HEAT AND THERMODYNAMIC CRITICAL FIELD FOR CALCIUM UNDER THE PRESSURE AT 120 GPa

Szczȩśniak, R.; Durajski, A. P.; Jarosik, M. W.

doi:10.1142/s0217984912500509

Cited by 19 publications

(6 citation statements)

References 20 publications

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“…Let us note that the thermodynamic properties of the superconducting state of lithium and calcium differ very significantly from the expectations of the BCS theory [35], [36], [37], [38], [39], [40]. It is also important to describe their properties, it is necessary to assume anomalously high values of the Coulomb pseudopotential (µ ⋆ ).…”

Section: Introductionmentioning

confidence: 99%

The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds

Szczȩśniak

Durajski

2013

Solid State Sciences

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Section: Introductionmentioning

confidence: 99%

The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds

Szczȩśniak

Durajski

2013

Solid State Sciences

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Section: Introductionmentioning

confidence: 99%

The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds

Szczȩśniak¹,

Durajski²

2013

Preprint

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The ab initio calculations suggest that the superconducting state in CaH6 under the pressure (p) at 150 GPa has the highest critical temperature among the examined hydrogen-rich compounds. For this reason, the relevant thermodynamic parameters of the superconducting state in CaH6 have been determined; a wide range of the Coulomb pseudopotential has been assumed: µ ⋆ ∈ 0.1, 0.3 . It has been found that: (i) The critical temperature (TC) changes in the range from 243 K to 180 K. (ii) The values of the ratio of the energy gap to the critical temperature (R∆ ≡ 2∆ (0) /kBTC ) can be found in the range from 5.42 to 5.02. (iii) The ratio of the specific heat jump (∆C (TC )) to the value of the specific heat in the normal state (C N (TC)), which has been represented by the symbol RC , takes the values from 3.30 to 3.18. (iv) The ratio RH ≡ TCC N (TC) /H 2 C (0), where HC (0) denotes the critical thermodynamic field, changes from 0.122 to 0.125. The above results mean that even for the strong electron depairing correlations the superconducting state in CaH6 is characterized by a very high value of TC, and the remaining thermodynamic parameters significantly deviate from the predictions of the BCS theory. The study has brought out the expressions that correctly predict the values of the thermodynamic parameters for the superconducting state in CaH6 and for the compounds: SiH4 (H2) 2 , Si2H6, B2H6, SiH4, GeH4, and PtH. Next, in the whole family of the hydrogen-rich compounds, the possible ranges of the values have been determined for TC, R∆, RC , and RH. It has been found that the maximum value of the critical temperature can be equal to 764 K, which very well correlates with TC for metallic hydrogen (p = 2 TPa). Other parameters (R∆, RC , and RH ) should not deviate from the predictions of the BCS theory more than the analogous parameters for CaH6.

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“…Due to the absence of the experimental value of the critical temperature, we assume the wide range of the Coulomb pseudopotential: µ ⋆ ∈ 0.1, 0.3 . This choice is connected with the fact that the value of the Coulomb pseudopotential in Ca and Li is high [23], [24]. For example:…”

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CaLi2 superconductor under the pressure of 100 GPa: the thermodynamic critical field and the specific heat

Szczęśniak,

Durajski,

Pach

2012

Preprint

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In the paper, the thermodynamic properties of the CaLi2 superconductor have been studied. It has been assumed the high value of the pressure: p = 100 GPa. The thermodynamic critical field (HC) and the specific heats for the superconducting and normal state (C S and C N ) have been obtained. The calculations have been made within the framework of the Eliashberg approach for the wide range of the Coulomb pseudopotential: µ ⋆ ∈ 0.1, 0.3 . It has been shown that the low-temperature critical field and the specific heat jump at TC strongly decrease if µ ⋆ increases. The value of the dimensionless ratio RC ≡ C S − C N /C N at the critical temperature differs significantly from the value predicted by the BCS model. In particular, the parameter RC decreases from 1.83 to 1.73 with the increase of the Coulomb pseudopotential value. In the paper, the interpolation formulas for the functions TC (µ ⋆ ) and RC (µ ⋆ ) have been also given.

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SPECIFIC HEAT AND THERMODYNAMIC CRITICAL FIELD FOR CALCIUM UNDER THE PRESSURE AT 120 GPa

Cited by 19 publications

References 20 publications

The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds

The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds

The thermodynamic properties of the high-pressure superconducting state in the hydrogen-rich compounds

CaLi2 superconductor under the pressure of 100 GPa: the thermodynamic critical field and the specific heat

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