Spin and charge excitations and photoemission spectra in 1D and 2D cuprates

We study spin and charge excitations and photoemission spectra in 1D and 2D cuprates by using the numerically exact diagonalization method on small clusters of the t-J model. We identify the bands with small and large dispersion recently observed in the angle-resolved photoemission spectroscopy (ARPES) experiments of the 1D cuprate SrCuO2 by Kim ct al. as those of spinon and holon with their energy scaled by t and J, respectively. The data are quantitatively analyzed by the numerical calculation based on the t-J model. The calculation is applied to the 2D cuprates. We find that in 2D, the ARPES spectrum depends strongly on the electron concentration: far away from half-filling, the spectrum is not much different from that in the Fermi liquid picture. On the other hand, near half-filling it becomes similar to that in 1D. We argue that the umklapp scattering causes the characteristic features in the spectrum near half-filling. (C) 1998 Elsevier Science Ltd. All rights reserved.