J. Phys. I France 7 (1997) 611-620
Anisotropy of Gap Parameter in Cuprate SuperconductorsS. Prakash
Department of Physics, Panjab University, Chandigarh-160014, India and Laboratoire de Physique du Solide, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex, France
(Received 3 June 1996, revised 19 September 1996, accepted 17 December 1996)
The anisotropy of gap parameter in cuprate superconductors is explained in the frame work of BCS theory using two-dimensional itinerant model of conduction electrons. The BCS gap equation at T=0 is solved in the first iteration approximation. The two-dimensional electron energy bands and electron-phonon interaction in tight-binding approximation are used. The explicit expression for the gap parameter (k) is evaluated for the Einstein model of the solid. It is found that (k) consists of a constant part and an oscillatory part which varies as sin 2kxa. The magnitude of oscillatory part is found to depend upon the cutoff energy , width of the singularity in the density of states near Fermi surface and overlap integral.
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