Pseudospin Models of Superconductors with Very Short Coherence Length
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We discuss a few models developed for description of superconductivity with very short coherence length and point out their formal equivalence to specific spin models, such as an anisotropic Heisenberg model (s = 1/2) with two- and four-spin exchange coupling and with fixed magnetization in the z-direction, an XY-Z model with single ion anisotropy and a Kondo-lattice model with anisotropic on-site exchange. New results concerning the phase diagram of the Hubbard model with strong attraction, the electromagnetic properties of systems with the first order superconducting transition and a possibility of local charge moment compensation in systems of coexisting bound pairs and itinerant electrons are presented.
- 74.20.-z: Theories and models of superconducting state
- 05.30.Jp: Boson systems(for static and dynamic properties of Bose-Einstein condensates, see 03.75.Hh and 03.75.Kk; see also 67.10.Ba Boson degeneracy in quantum fluids)
- 71.28.+d: Narrow-band systems; intermediate-valence solids(for magnetic aspects, see 75.20.Hr and 75.30.Mb in magnetic properties and materials)
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