A possible non-pairing mechanism for high-Tcperfect conductors in two dimensions

Abstract

The authors have generalised Frohlich's model of 1D superconductivity to systems with 2D layers associated with nearly nested Fermi surfaces. In the ground state phonons with wavevectors that span opposite sides of the Fermi surface are found to have coherent, macroscopic amplitudes when they are coupled resonantly to the corresponding electron density waves, Umklapp processes notwithstanding. These quantum mechanical wave amplitudes constitute the order parameter of the system, decreasing to zero as T to Tc, the critical temperature. They also give rise to a temperature-dependent energy gap. In the absence of Umklapp processes, such a gap would lead to perfect conductivity for T<Tc, as for the original 1D version given by Frolich. The scale of Tc is determined by the much higher epsilon F, rather than by omega D; hence also the absence of an isotope effect. This model, with independent electrons and phonons and the associated order parameter, should serve as a new and significantly different zeroth-order system, a springboard from which BCS pairing could then be built.