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 kz 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_. 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.