High-temperature superconductivity of diamagnetic heavy electrons: Crossover between Cooper pairing and Bose condensation
Fusayoshi J. Ohkawa
DOI 10.1103/PhysRevB.46.11965 · Physical Review B
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Abstract
A negative-U Hubbard-type model with nearest-neighbor weak repulsion is studied in the 1/d expansion, with d being the spatial dimensionality. The leading-order effects in 1/d are ‘‘Kondo’’-effect-type local charge fluctuations and mean-field-approximation-type charge-density waves and superconductivity. A ‘‘local’’ Kondo temperature TK is defined to show an energy scale of the charge fluctuations, which are responsible for the formation of diamagnetic heavy-electron systems. The bandwidth of the heavy electrons is about 4kBTK. Superconductivity occurs when the system is away from half filling. Its critical temperature Tc is highest in the crossover regime as a function of ‖U‖, where ‖U‖ is as large as the bare bandwidth of electrons. The superconductivity in such a regime is of a crossover type between Cooper pairing and Bose-Einstein condensation. On the basis of Varma’s proposal that a negative U results from nonlinear screening [Phys. Rev. Lett. 61, 2713 (1988)], it is argued that superconducting BaxK1−xBiO3 with Tc≊30 K are diamagnetic heavy-electron systems with TK≊(2–5)×103 K.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| BaxK1-xBiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 30 | Pressure not reported | unknown |
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