Browsing by Author "de Llano, M."

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Are Preformed Cooper Pairs The Cause For The Pseudogap in Superconductors?
(2014) Mamedov, T. A.; de Llano, M.; JFS-2792-2023
A weak-coupling scenario wherein bosonic preformed electron pairs emerge upon cooling from two-electron correlations can explain the pseudogap phase consisting of segments where a Bogoliubov-like energy-momentum relation gapped spectrum alternates with a normal ungapped one. Bose-Einstein condensation (BEC) of preformed pairs interacting with the background fermions leads to either [GRAPHICS] - or [GRAPHICS] -wave-like superconducting gaps, the result being sensitive to the magnitude of the total number density of pairs [GRAPHICS] at which BEC occurs and becomes possible already for a moderately anisotropic [GRAPHICS] -wave pairing of fermions repelling each other via isotropic coulombic forces. The present model is compatible with the coexistence of pseudogap and of superconductivity phenomena.
Kink Structure in Nodal Quasiparticle Dispersion in a Boson-Fermion Model of Superconductivity
(2017) Mamedov, T. A.; de Llano, M.
At temperatures below a certain T *, single unbound electrons in high-T-c cuprates are assumed to coexist with bosonic Cooper pairs (CPs) of electrons emerging incoherently from an attractively interacting system of fermions. Due to both simultaneous interfermion attractions (as in BCS theory) and depairings, the conductive electrons at temperatures higher than the T-c of a Bose-Einstein condensation of preformed CPs fluctuate unceasingly between single-fermionic states and states of two bound electrons considered actual bosonic objects. We explore how these interactions in a background of such"frustrated electrons," i. e., those electrons appearing both as unbound (free) electrons and as constituents of the bosonic CPs, affect the dispersion of a fermion moving in the assembly of other electrons and, in particular, how the recently observed "kinks" in the dispersion curves emerge.
Preformed Cooper Pairs as Origin of Pseudogap in Cuprates
(2015) Mamedov, T. A; de Llano, M.; JFS-2792-2023
A weak-coupling scenario wherein bosonic preformed electron pairs emerge upon cooling from two-electron correlations can explain the pseudogap phase consisting of segments where a Bogoliubov-like energy-momentum relation gapped spectrum alternates with a normal ungapped one. Bose-Einstein condensation (BEC) of preformed pairs interacting with the background fermions leads to either d- or s wave-like superconducting gaps, the result being sensitive to the magnitude of the total number density of pairs n (B) at which BEC occurs and becomes possible already for a moderately anisotropic s wave pairing of fermions repelling each other via isotropic coulombic forces. The present model is compatible with the coexistence of both pseudogap and of superconductivity phenomena.