Influence of the Third Dimension of Quasi-Two-Dimensional Cuprate   Superconductors on Angle-Resolved Photoemission Spectra
  Angle-resolved photoemission spectroscopy (ARPES) presents significant simplications in analyzing strictly two-dimensional (2D) materials, but even the most anisotropic physical systems display some residual three-dimensionality. Here we demonstrate how this third dimension manifests itself in ARPES spectra of quasi-2D materials by considering the example of the cuprate Bi$_2$Sr$_2$CaCu$_2$O$_{8}$ (Bi2212). The intercell, interlayer hopping, which is responsible for $k_z$-dispersion of the bands, is found to induce an irreducible broadening to the ARPES lineshapes with a characteristic dependence on the in-plane momentum $k_\parallel$. Our study suggests that ARPES lineshapes can provide a direct spectroscopic window for establishing the existence of coherent c-axis conductivity in a material via the detection of this new broadening mechanism, and bears on the understanding of 2D to 3D crossover and pseudogap and stripe physics in novel materials through ARPES experiments. 
A. Bansil, M. Lindroos, S. Sahrakorpi, and R.S. Markiewicz