Nonlocal excitations and 1/8 singularity in cuprates

Abstract

To be published in the Journal of the Korean Physical Society) Momentum-dependent excitation spectra of the two-dimensional Hubbard model on the square lattice have been investigated at zero temperature on the basis of the full self-consistent projection operator method in order to clarify nonlocal effects of electron correlations on the spectra. It is found that intersite antiferromagnetic correlations cause shadow bands and enhance the Mott-Hubbard splittings near the half-filling. Furthermore nonlocal excitations are shown to move the critical doping concentration δ * h , at which the singular quasiparticle peak is located just on the Fermi level, from δ * h = 0.153 (the single-site value) to δ * h = 0.123. The latter suggests the occurance of an instability such as the stripe at δ * h = 1/8.