Depairing and Bose–Einstein condensation temperatures in a boson–fermion superconductor model with Coulomb effects

Abstract

An extended boson–fermion (BF) model is introduced describing the evolution of attractively interacting single electrons into a binary mixture of unpaired electrons plus incoherent bosonic Cooper pairs as absolute temperature is lowered. The new model is employed to determine how the system, upon cooling, exhibits critical temperatures for: a) incoherent boson formation below as well as b) for creating a coherent boson fluid below . Critical temperatures and are related with the dynamical parameters of the attractively interacting fermion system. It is shown that the introduction of a uniform Coulomb interaction in an anisotropic BF binary gas mixture model allows finding not only a self-consistent description of a pseudogap and a dome-shaped -vs-doping behaviour, but also to predict, even in a phonon-mediated many-electron dynamics, of an energy–momentum dispersion that is either gapped or not depending on direction. This manifests itself in high- superconductors as curves in momentum space along which the superconducting gap vanishes, hence giving rise to the so-called “Fermi arcs” observed in angle-resolved-photoemission spectroscopy experiments.

Keywords:

• boson–fermion models
• boson formation
• Bose–Einstein condensation
• pseudogap
• fermi arcs

Acknowledgments

We thank D.M. Eagles for a thorough reading of the manuscript and for numerous comments, as well as E. Mazur for e-correspondence. TAM thanks the Institute of Physics of Azerbaijan for granting him academic leave at Baskent University in Ankara, Turkey. MdeLl thanks UNAM-DGAPA-PAPIIT (Mexico) for its support via grant IN102011.

Notes

Permanent address: Institute of Physics, Academy of Sciences of Azerbaijan, 370143 Baku, Azerbaijan.