ENHANCEMENT OF FERMI VELOCITY BY ELECTRON-ELECTRON INTERACTIONS, AND THE TRANSPORT-PROPERTIES OF HIGH-T(C) SUPERCONDUCTORS

We consider a composite quasi-2D electron gas, consisting of metallic layers of width d and a background dielectric constant epsilon1, separ ated by layers with dielectric constant epsilon2, where d > a0, a0 = H BAR2epsilon1/me2 and epsilon2 >> epsilon 1. We show that the Coulomb i nteraction renormalizes the velocity v(k) for k almost-equal-to k(F), and v(k(F)) is increased by a factor close to epsilon2/epsilon1. The p eak of v(k) around k = k(F) is very narrow. Thus the anomalous propert ies of an electron gas calculated by Lindhard in 1954 for an unscreene d electron gas, can persist, under special conditions, even if screeni ng is taken into account. We employ this theory to the normal-state pr operties of the cuprates. We find that the conductivity is increased b y a factor of: [v(k(F))/v(0)(k(F))]2 almost-equal-to [epsilon2/epsilon 1]2 due to the velocity renormalization and the resistivity due to ela stic scattering becomes temperature-dependent. We account for the cond uctivity anisotropy, Hall constant, thermoelectric power, and London p enetration depth. Measurements of the Fermi velocity by N. Hass, emplo ying Andreev reflection, indicate a significant increase in the veloci ty close to the Fermi level. This velocity renormalization increases T (c) significantly.