The polarizability of the Lochon-Fermion interaction in the cuprate superconductors

Abstract

The cuprates are close to metal-insulator transition and the stability of the insulating or the metallic phase depends on the degree of doping. Consistent with charge transfer degrees of freedom, an interaction mechanism involving lochons (composities of a pair of fermions in the singlet state) and free fermions was suggested for these systems. The process involves the splitting of lochons into a pair of fermions and the confluence of a fermion pair to give a lochon. In the present paper, the self energy of lochons is calculated using the Nambu formalism. The imaginary part of the polarizability connected with these charge excitations is found to have the form hypothesised in a recent phenomenological approach to explain the anomalous properties of the normal state. Thus fermion-lochon interaction is important for both the normal and superconducting states of cuprates.