Two-Fermi-liquid model for high-T_c superconductivity involving suppression of tunneling by decoherence

Abstract

We consider a model system of two interacting Fermiliquids, one of which is light and the other much heavier. In the normal state the lighter component provides a quantum mechanical bath coupled 'ohmically' to the heavier component in the sense of Caldeira and Legett, suppressing thereby the band (tunnelling) matrix elements of the heavier component. Thus we lose the energy of delocalization. On the other hand, a superconducting ordering stiffens the bath spectral function at low energies and so restores the tunnelling. The resulting regain of the delocalization energy boothstraps so as to stabilize the superconducting order that caused it. It is conceivable that the motions parallel to the easy ab-plane and along the hard c-axis may also effectively correspond to the light and the heavy Fermi-liquids, respectively.