Anisotropy of acceptor states in lightly doped cuprate superconductors

We investigate the role of short wavelength antiferromagnetic correlations in the spatial structure of acceptor states doped into a two-dimensional Mott-Hubbard antiferromagnetic insulator. We extend the traditional effective mass approximation, by using the Green's function formalism and its spectral representation, and we show that when the electronic scattering at the ordering wavevector Q = (π,π) is strong enough to produce a momentum dependent scattering rate, Γk, the corresponding acceptor state envelope wavefunction becomes spatially anisotropic. Finally, we discuss the connection between our results and photoemission spectra in lightly doped La2-xSrxCuO4. (paper)