Optical response of Ba1−xKxBiO3: Evidence for an unusual coupling mechanism of superconductivity
H. J. Kaufmann, Oleg V. Dolgov, E. K. H. Salje
DOI 10.1103/PhysRevB.58.9479 · Physical Review B
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Abstract
We have analyzed optical reflectivity data for Ba1−xKxBiO3 in the far-infrared region using Migdal-Eliashberg theory and found it inconsistent with standard electron-phonon coupling: Whereas the superconducting state data could be explained using moderate coupling, λ=0.7, the normal state properties indicate λ<~0.2. We have found that such behavior could be understood using a simple model consisting of weak standard electron-phonon coupling plus weak coupling to an unspecified high energy excitation near 0.4 eV. This model is found to be in general agreement with the reflectivity data, except for the predicted superconducting gap size. The additional high energy excitation suggests that the dominant coupling mechanism in Ba1−xKxBiO3 is not standard electron-phonon.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Ba1-xKxBiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 30 | Pressure not reported | unknown |
| Ba0.6K0.4BiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 28 | Pressure not reported | unknown |
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