Electron momentum distribution function in the t-t′-J model

We study the electron momentum distribution function (EMDF) for the two-dimensional t-t'-J model doped with one hole on finite clusters by the method of twisted boundary conditions. The results quantitatively agree with our analytical results for a single hole in the antiferromagnetic background, based on the self-consistent Born approximation (SCBA). Moreover, within the SCBA an anomalous momentum dependence of EMDF is found, pointing to an emerging large Fermi surface. The analysis shows that the presence of next-nearest-neighbor (NNN) hopping terms changes EMDF only quantitatively if the ground state (GS) momentum is at (pi/2,pi 2) and qualitatively if the GS momentum is shifted to (pi,0). (C) 2000 Elsevier Science B.V. All rights reserved.