POSSIBILITY OF THE NONPHONON MECHANISM OF SUPERCONDUCTIVITY IN A LAYERED FERMI-LIQUID

Superconductivity and the metal-insulator (MI) phase transition in a l ayered two-dimensional (2D) electron liquid, taking into account elect ron-correlation effects and spin-density fluctuations, have been consi dered by means of the Fermi-liquid approach. It is shown that the elec tron-electron interaction mediated by electron-hole excitations in a l ayered 2D correlated Fermi liquid can induce the MI phase transition. The possibility of superconductivity mediated by the electron-hole exc itations in the case of the dynamical suppression of the vertex correc tion by the high-frequency plasma excitations is discussed. The depend ence of the transition temperature T-c on the carrier (doping) density , the inter layer spacing and the dielectric constant is obtained. It is also found that the superconductivity transition temperature at the strong coupling can be given by T-c similar to n(s)/m while it is gi ven by a BCS-like formula T-c similar to 1.13 omega(c) exp(-1/lambda(e ff)) at the weak coupling.