Evolution of Mid-gap States and Residual 3-Dimensionality in Cuprates*

We have carried out extensive first principles doping-dependent computations of angle-resolved photoemission (ARPES) intensities in Bi$_2$Sr$_2$CaCu$_2$O$_8$ (Bi2212) and La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) over a wide range of binding energies.$^{1,2,3}$ Intercell hopping and the associated 3-dimensionality, which is usually neglected in discussing cuprate physics, is shown to play a key role in shaping the ARPES spectra. Despite the obvious importance of strong coupling effects (e.g. the presence of a lower Hubbard band coexisting with mid-gap states in the doped insulator), a number of salient features of the experimental ARPES spectra of LSCO are captured to a surprising extent when $k_z$-dispersion is properly included in the analysis. \\ \\ 1. S. Sahrakorpi, et al., Phys. Rev. Lett. 95, 157601 (2005).\\ 2. A. Bansil, et al., Phys. Rev. B 71, 012503 (2005).\\ 3. A. Bansil, et al., New Journal of Physics 7, 140 (2005); http://www.iop.org/EJ/abstract/1367-2630/7/1/140.