Role of kz-dispersion in photoemission from quasi-2D cuprates

Abstract

Abstract We discuss how the effects of dispersion of electronic states with k z , which have largely been neglected in discussing the cuprates, play out in the analysis and interpretation of the angle-resolved photoemission (ARPES) spectra from quasi-two-dimensional (2D) materials. Illustrative results on Bi 2 Sr 2 CaCu 2 O 8 (Bi2212) and La 2− x Sr x CuO 4 (LSCO) are presented. k z -dispersion induces an irreducible width to ARPES spectral peaks. This width does not have its origin in a scattering mechanism. It is also manifest in ARPES photointensities for emission from the Fermi energy, where the Fermi surface (FS) maps so obtained display k ∥ -dependent widths, which can be quite large especially in the antinodal region. The first principles photointensities computed in LSCO within the local-density approximation (LDA) based band theory framework are found to reproduce many salient features of the experimental ARPES spectra, even in the underdoped regime, suggesting that some sort of a generalized Luttinger theorem continues to hold in the presence of strong electron correlations. In the lightly doped insulating LSCO, we show via tight-binding model computations that effects of k z -dispersion can give insight into characteristic broadenings observed in the ARPES features associated with the lower Hubbard band and the mid-gap states.