The pseudogap mode as long-lived states of noncoherent pairs with large momenta

摘要

The mirror nesting of the Fermi contour of a quasi-two-dimensional electronic system and the presence of at least one negative eigenvalue of the Fourier transform of interaction energy are sufficient conditions for the formation of bound states of the relative motion of pairs with large total momenta. As distinct from pairing by attractive interactions, the wave functions of such pairs have alternating signs and lines of zeros that twice intersect the Fermi contour in the regions of definition of relative motion momenta. The total number of intersection points between the line of zeros and the Fermi contour is determined by symmetry of a linear combination of the wave functions of crystallographically equivalent pairs. Long-lived quasi-stationary states exist in the form of noncoherent pairs with different but close momenta and cause substantial suppression of the density of one-particle states (the appearance of a pseudogap) over a fairly wide energy range. The upper temperature bound of the pseudogap is determined by the decay of pairs, and the lower bound, by phase coherence disturbance when pairs leave the condensate that is formed at some optimum pair momentum value owing to mirror nesting. (C) 2004 MAIK "Nauka / Interperiodica".