|
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. We demonstrate how this third dimension manifests
itself in ARPES spectra of quasi-2D materials by considering the examples
of Bi2Sr2CaCu2O8 (Bi2212) and La2-xSrxCuO4 (LSCO). The intercell hopping,
which is responsible for kz-dispersion of the bands, is found to induce an
irreducible broadening to the ARPES lineshapes with a characteristic
dependence on the in-plane momentum. The ARPES lineshapes can thus
provide a direct spectroscopic window for establishing the existence of
c-axis conductivity in a material via the detection of this new broadening
mechanism, and bear on the understanding of 2D to 3D crossover and
pseudogap and stripe physics in novel materials. Our analysis indicates
that mid-gap states, which are first created when the Mott insulator is
doped with holes, may be viewed as preformed metallic states.
**Work done iIn collaboration with V. Arpiainen, H. Lin, M. Lindroos, R.S. Markiewicz, S. Sahrakorpi. |