Spectral function of a hole in a Hubbard antiferromagnet

Abstract

The Green's function G(k,\ensuremath{\omega}) is calculated for a hole in a Hubbard antiferromagnet by a new nonperturbative, variational method for an infinite square lattice. The quasiparticle and excited-state wave functions show that the substantial structure in the ``incoherent'' spectrum is related to string states for large U. The strength of the quasiparticle pole and the anisotropic effective mass are obtained as a function of (U/t). The quasiparticle lifetime is infinite for most k.