On the superconducting state in Ba^sub 0.6^K^sub 0.4^BiO^sub 3^perovskite oxide

We report study on the superconducting state in Ba0.6K0.4 BiO3 (BKBO) perovskite oxide, motivated by the inconclusive results on the pairing mechanism in this compound. Our investigations are conducted within the Migdal-Eliashberg formalism, to account for the phonon-mediated superconducting phase....

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Bibliographic Details
Published in:	Physica. B, Condensed matter Vol. 536; p. 676
Main Authors:	Szczesniak, D, Kaczmarek, AZ, Drzazga, EA, Szewczyk, KA, Szczesniak, R
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier BV 01-05-2018
Subjects:	Band gap Coupling Critical field (superconductivity) Critical temperature Dimensionless analysis Energy gap Isotope effect Isotopes Oxygen isotopes Perovskite Perovskites Superconductivity Thermodynamics Transition temperature
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Summary:	We report study on the superconducting state in Ba0.6K0.4 BiO3 (BKBO) perovskite oxide, motivated by the inconclusive results on the pairing mechanism in this compound. Our investigations are conducted within the Migdal-Eliashberg formalism, to account for the phonon-mediated superconducting phase. The considered doping level of the discussed material corresponds to the highest critical temperature in this compound, and allows simultaneous analysis of the oxygen isotope effect, for the O16 and O18 isotopes, respectively. We found that such effect is particularly visible for the critical values of the Coulomb pseudopotential μC, which equals to 0.18 for the O16 and 0.16 for the O18 isotope in BKBO. Moreover, we determine the size of the superconducting energy band gap (∆g) and note that obtained values (9.68 meV and 9.55 meV for the O16 and O18, respectively) are in good agreement with the experimental predictions which give ∆g ~ 8.68 meV. Finally, we calculate the characteristic dimensionless parameters, such as the zero-temperature energy gap to the critical temperature, the ratio for the specific heat, as well as the ratio associated with the zero-temperature thermodynamic critical field, which suggest occurrence of the strong-coupling and retardation effects within the phonon-mediated scenario in the analyzed material. Where possible the dimensionless ratios are compared to the experimental estimates, and agrees with these which account for the strong-coupling character of the BKBO superconductor.
ISSN:	0921-4526 1873-2135