arXiv subjects

S. G. Sharapov

Publications and source records attributed to S. G. Sharapov.

57 records · Page 4Linked to original sources

arXiv1997

Superconducting Condensate Formation in Metallic Systems with Arbitrary Carrier Density (review)

This article gives a contemporary and to some extent pedagogical review of the current theoretical understanding of the formation of the superconducting state in metallic systems with a variable density of carriers. We make an attempt to describe the crossover from the Bose-Einstein condensation type (small densities) to the Bardeen-Cooper-Schrieffer one (large densities). The functional methods are used throughout the treatment. The most of the results are considered in a review form for the first time. Some of them (in particular, the possible opening of a pseudogap) are used to explain the experimental data avaliable for high-temperatures superconductors.

cond-mat.supr-con↗

arXiv1997

Phase diagram in 2D Fröhlich model of metal at arbitrary carrier density: pseudogap versus doping

It is shown that in 2D system of the fermions with simplest indirect boson-induced attraction (through the Einstein phonon exchange as an example) along with the normal and superconducting phases there arises a new (called "abnormal normal" or pseudogap) one where the absolute value of the order parameter is finite but its phase is a random quantity. It is important that this new phase really exists at low carriers density only, i.e. it shrinks when doping increases. The relevance of the results obtained with dependence of pseudogap on doping in high-temperature superconductors is speculated.

cond-mat.supr-con↗

arXiv1996

Crossover from BCS to Composite Boson (Local Pair) Superconductivity in Quasi-2D systems

The crossover from cooperative Cooper pairing to independent bound state (composite bosons) formation and condensation in quasi-2D systems is studied. It is shown that at low carrier density the critical superconducting temperature is equal to the temperature of Bose-condensation of ideal quasi-2D Bose-gas with heavy dynamical mass, meanwhile at high densities the BCS result remains valid. The evident nonmonotoneous behaviour of the critical temperature as function of the coupling constant (the energy of the two particle bound state) is a qualitative difference of quasi-2D crossover from 3D one.

cond-mat↗