VELOCITY RENORMALIZATION NEAR THE MOTT TRANSITION IN A PERFECTLY ORDERED LATTICE (II)

We consider a medium-density electron gas, near the Wigner-Mott transi tion, immersed in a medium with a background dielectric constant epsil on0(q, omega) that is very large at q = 0, omega = 0, but falls sharpl y with increasing q and/or omega. We consider the dependence of the sc reening parameter for state k on the energy of this state. We find tha t the electronic velocity is enhanced considerably at k = k(F), somewh at similar to the enhancement found by Lindhard in 1954 for an unscree ned electron gas. We use parameters applicable to high-T(c) cuprates. We find that the maximum of upsilon(k) around k(F) is very sharp, the width being a few meV, somewhat smaller than the frequency at which th e dielectric constant epsilon0(q, omega) drops. We relate this velocit y peak to the normal-state transport properties of the cuprates and se veral other systems, and to the superconductivity. We point out specif ic experiments that suggest a large enhancement of upsilon(F).