Central peak in the pseudogap of high Tc superconductors
Department of Physics, Faculty of Science, University of
Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
Revised: 9 May 2005
Published online: 11 August 2005
We study the effect of antiferromagnetic (AF) correlations in the three-band Emery model, with respect to the experimental situation in weakly underdoped and optimally doped BSCCO. In the vicinity of the vH singularity of the conduction band there appears a central peak in the middle of a pseudogap, which is in an antiadiabatic regime, insensitive to the time scale of the mechanism responsible for the pseudogap. We find a quantum low-temperature regime corresponding to experiment, in which the pseudogap is created by zero-point motion of the magnons, as opposed to the usual semiclassical derivation, where it is due to a divergence of the magnon occupation number. Detailed analysis of the spectral functions along the – line show significant agreement with experiment, both qualitative and, in the principal scales, quantitative. The observed slight approaching-then-receding of both the wide and narrow peaks with respect to the Fermi energy is also reproduced. We conclude that optimally doped BSCCO has a well-developed pseudogap of the order of 1000 K. This is only masked by the narrow antiadiabatic peak, which provides a small energy scale, unrelated to the AF scale, and primarily controlled by the position of the chemical potential.
PACS: 74.72.-h – Cuprate superconductors (high-Tc and insulating parent compounds) / 71.27.+a – Strongly correlated electron systems; heavy fermions / 71.10.Ay – Fermi-liquid theory and other phenomenological models
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005