We analyze a boson-fermion model that accounts for the electrostatic potential of the out-of-plane dopant atoms. We investigate whether this approach may explain recent experimental results obtained for the Bi-based high-temperature superconductors. We demonstrate that in contradistinction to purely fermionic models, even weak electrostatic potential of the dopant atoms may be responsible for a significant modulation of the superconducting order parameter.
Experimental results concerning persistent currents in small rings threaded by a magnetic flux do not agree with theoretical predictions, especially for experiments performed in diffusive regime. This suggests important role of disorder in these experiments. In this paper we demonstrate how impurities present in ring modify the persistent current by generating or enhancing charge density waves. The electronic correlations are taken into account for both repulsive as well as attractive electron-electron interaction. The calculations are carried out for one-dimensional rings consisting of up to 12 lattice sites using Lanczös exact diagonalization approach, and for finite-width much larger rings using the Bogolyubov-de Gennes equations.
We investigate the vortex structure in the Penson-Kolb model with and without impurities. We focus on the consequences arising from the non-local field-dependent pairing interaction for the vortex profile, current distribution, and the local density of states.
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