Anisotropy of Gap Parameter in Cuprate Superconductors

S. Prakash

doi:doi:10.1051/jp1:1997179

Numéro		J. Phys. I France Volume 7, Numéro 4, April 1997


Page(s)		611 - 620
DOI		https://doi.org/10.1051/jp1:1997179

DOI: 10.1051/jp1:1997179
J. Phys. I France 7 (1997) 611-620

Anisotropy of Gap Parameter in Cuprate Superconductors

S. 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)

Abstract
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 $\Delta^0$ (k) is evaluated for the Einstein model of the solid. It is found that $\Delta^0$ (k) consists of a constant part and an oscillatory part which varies as sin ²k_xa. The magnitude of oscillatory part is found to depend upon the cutoff energy $\hbar \omega_{\rm c}$ , width of the singularity in the density of states near Fermi surface and overlap integral.