Influence of the third dimension of quasi-two-dimensional cuprate superconductors on angle-resolved photoemission spectra

Angle-resolved photoemission spectroscopy (ARPES) presents significant simplifications 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 Bi2Sr2CaCu2O8 (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 line shapes with a characteristic dependence on the in-plane momentum k(parallel to). Our study suggests that ARPES line shapes can provide a direct spectroscopic window for establishing the existence of coherent c-axis conductivity in a material via the detection of this broadening mechanism, and bears on the understanding of 2D to 3D crossover and pseudogap and stripe physics in novel materials through ARPES experiments.