1. Superconducting energy gap in $\rm Ba_{1-x}K_xBiO_3$: Temperature dependence
- Author
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Szabo, F., Samuely, P., Bobrov, N. L., Marcus, J., Escribe-Filippini, C., and Affronte, M.
- Subjects
Condensed Matter - Superconductivity - Abstract
The superconducting energy gap of $\rm Ba_{1-x}K_xBiO_3$ has been measured by tunneling. Despite the fact that the sample was macroscopically single phase with very sharp superconducting transition $T_c$ at 32~$K$, some of the measured tunnel junctions made by point contacts between silver tip and single crystal of $\rm Ba_{1-x}K_xBiO_3$ had lower transition at 20~$K$. Local variation of the potassium concentration as well as oxygen deficiency in $\rm Ba_{1-x}K_xBiO_3$ at the place where the point contact is made can account for the change of $T_c$. The conductance curves of the tunnel junctions reveal the BCS behavior with a small broadening of the superconducting-gap structure. A value of the energy gap scales with $T_c$. The reduced gap amounts to $2\Delta/kT_c = 4\div 4.3$ indicating a medium coupling strength. Temperature dependence of the energy gap follows the BCS prediction., Comment: 2 pages, 3 figures
- Published
- 2017
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