Electron momentum distribution in underdoped cuprates

We investigate the electron momentum distribution function (EMD) in a weakl y doped two-dimensional quantum antiferromagnet (AFM) as described by the t -J model. Our analytical results for a single hole in an AFM based on the s elf-consistent Born approximation (SCBA) indicate an anomalous momentum dep endence of EMD showing "hole pockets" coexisting with a signature of an eme rging large Fermi surface. The position of the incipient Fermi surface and the structure of the EMD is determined by the momentum of the ground state. Our analysis shows that this result remains robust in the presence of next -nearest neighbor hopping terms in the model. Exact diagonalization results for small clusters are with the SCBA reproduced quantitatively.