Extended BCS-Bose crossover
Por:
Chávez I., García L.A., Grether M., de Llano M., Tolmachev V.V.
Publicada:
1 ene 2018
Ahead of Print:
1 ene 2017
Resumen:
Applying the generalized Bose-Einstein condensation (GBEC) formalism, we extend the BCS-Bose crossover theory by explicitly including hole Cooper pairs (2hCPs). From this, follows a phase diagram with two pure phases, one with 2hCPs and the other with electron Cooper pairs (2eCPs), plus a mixed phase with arbitrary proportions of 2eCPs and 2hCPs. The special-case phase when there is perfect symmetry, i.e., with ideal 50-50 proportions between 2eCPs and 2hCPs, corresponds to the usual BCS-Bose crossover. Explicitly including 2hCPs yields an extended BCS-Bose crossover which predicts improved Tc/TF values for some conventional superconductors (i.e., with electron-phonon dynamics) when compared with experiment. To do this, we employ the BCS dimensionless coupling constant ?BCS via the BCS gap equation and compare with the Bogoliubov et al. upper limit ?BCS = 1/2. Another phase diagram presented exhibits experimental Tc/TF values for some conventional superconductors for arbitrary proportions between 2eCPs and 2hCPs as function of n = n/nf - 1, where n is the electron concentration and nf that of unbound electrons at T = 0. The extended crossover is compared with experimental Tc/TF values as well as to the gap-to-Tc ratio. © Springer Science+Business Media, LLC 2017.
Filiaciones:
Chávez I.:
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo. Postal 70-360, Mexico City, 04360, Mexico
García L.A.:
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo. Postal 70-360, Mexico City, 04360, Mexico
Grether M.:
Facultad de Ciencias, Universidad Nacional Autónoma de México, México City, 04510, Mexico
de Llano M.:
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo. Postal 70-360, Mexico City, 04360, Mexico
Tolmachev V.V.:
N.E. Baumann State Technical University, Moscow, Russian Federation
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