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Research & Reviews: Journal of Material Sciences | ISSN: 2321-6212 | Volume 6

Theoretical, Materials and Condensed Matter Physics

International Conference on

November 26-28, 2018 | Los Angeles, USA

Cooper pairs in superconductivity in a generalized BEC theory

I Chávez, LA García, M Grether

and

M de Llano

Universidad Nacional Autónoma de México, México

he generalized Bose-Einstein condensation (GBEC) theory subsumes as special cases both BCS and BEC, among other

theories. It hinges on three separate new ingredients: i) treating Cooper pairs (CPs) as

actual

bosons as distinct from BCS

pairs which strictly speaking are not bosons; ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with the

usual two-electron ones (2eCPs); and iii) incorporating in the resulting ideal

ternary

boson-fermion (BF) gas specific vertex

interactions that drive formation/dis-integration processes of both kinds of CPs. Here we extend the BCS-Bose crossover

theory by

explicitly

including 2hCPs. This leads to a phase diagram with two pure phases, one with 2eCPs and the other with

2hCPs, plus a mixed phase with arbitrary proportions of both. The special-case phase with a 50-50 mixture of both 2e/2hCPs

gives the usual

unextended

BCS-Bose crossover theory. Furthermore, if

and

are respectively the critical and the Fermi

temperatures, it predicts

values for the elemental superconductors Al, In, Sn, Pb, Hg, and Nb comparing quite well with

experiment and notably much better than BCS predictions. Also shown is a phase diagram of the dimensionless energy gap at

zero-temperature Δ(0)/

vs n/n

, where

is the Fermi energy. We do this for the 50-50 case as well as for the pure 2eCPs

and 2hCPs cases separately. It is thus unequivocally shown that if one ignores 2hCPs the energy gap lies substantially below the

50-50 case which already roughly reproduces the data.

Biography

I Chávez MS and BS have completed his Doctoral degree in the Material Sciences and Engineering Research Graduate Program at the National Autonomous

University of Mexico (UNAM, in Spanish) with the thesis titled “

A new dimensionless coupling constant in superconductivity

.” He is also a Laboratory Assistant at

the School of Sciences at UNAM.

I Chávez et al., Res. Rev. J Mat. Sci. 2018, Volume 6

DOI: 10.4172/2321-6212-C10-041