EFFECT OF ANISOTROPY ON THE ENERGY-GAP AND THE CRITICAL-TEMPERATURE IN A STRONGLY COUPLED LAYERED SUPERCONDUCTOR

Authors
Citation
Ep. Nakhmedov, EFFECT OF ANISOTROPY ON THE ENERGY-GAP AND THE CRITICAL-TEMPERATURE IN A STRONGLY COUPLED LAYERED SUPERCONDUCTOR, Physical review. B, Condensed matter, 54(9), 1996, pp. 6624-6631
Citations number
38
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
01631829
Volume
54
Issue
9
Year of publication
1996
Pages
6624 - 6631
Database
ISI
SICI code
0163-1829(1996)54:9<6624:EOAOTE>2.0.ZU;2-W
Abstract
The Eliashberg theory is applied to study the critical temperature and a gap anisotropy of strongly coupled layered superconductors. The ele ctron-ion pseudopotential, the electron, and the phonon energy spectra an proposed to be anisotropic in layered crystals with an open Fermi surface. The anisotropic electron-phonon spectral density [alpha(2)F(z )](pz) is found to be expanded in cos(np(z)d) functions. Such an expre ssion for [alpha(2)F(z)](pz) demands the energy gap Delta(p(z),omega) to present also as an expansion in the harmonic functions. Therefore, the value of the energy gap along the c axis should display p(z) depen dence. The value of Delta differs from that obtained by in-plane measu rements. By using McMillan's method we present each amplitude Delta(n) (omega) in the harmonic expansion of the energy gap Delta(p(z),omega) by trial function. The infinite set of coupled homogeneous equations f or Delta(0), Delta(1), Delta(2),... is obtained, the solution of which should yield the critical temperature. We estimate only those equatio ns which include the three amplitudes, Delta(0), Delta(1), and Delta(2 ), in the harmonic expansion of the energy gap. An approximate calcula tion of T-c shows that the critical temperature must be enhanced due t o the influence of anisotropy.