THEORY OF THE PSEUDOGAP FORMATION IN 2D ATTRACTING FERMION SYSTEMS

The two-dimensional fermion system with the indirect Einstein phonon-e xchange attraction and additional local four-fermion interaction is co nsidered. It is shown that as a result of the attraction between fermi ons, the normal phase of such a system is divided into two regions. In one of them, called the pseudogap region, the absolute value of the o rder parameter exists as essentially nonzero value, but its phase is a random quantity. It is important that in the case of attraction due t o the phonons, this abnormal region appears at rather low carrier conc entrations, i.e., it decreases appreciably with increasing doping. The relevance of the results obtained for high-temperature superconductor s is speculated. (C) 1998 American Institute of Physics. [S1063-7761(9 8)01708-9].