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 cl usters of the t-J model. We identify the bands with small and large dispers ion recently observed in the angle-resolved photoemission spectroscopy (ARP ES) experiments of the 1D cuprate SrCuO2 by Kim ct al. as those of spinon a nd holon with their energy scaled by t and J, respectively. The data are qu antitatively 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 ARPE S spectrum depends strongly on the electron concentration: far away from ha lf-filling, the spectrum is not much different from that in the Fermi liqui d picture. On the other hand, near half-filling it becomes similar to that in 1D. We argue that the umklapp scattering causes the characteristic featu res in the spectrum near half-filling. (C) 1998 Elsevier Science Ltd. All r ights reserved.