Electronic excitations in strongly correlated systems; 1D vs. 2D

Abstract

The single-particle, spin and charge excitation spectra in one- (1D), two-dimensional (2D) and two-leg-ladder t- J models are presented in the exact diagonalization technique. In 1D, the spin-charge separation is obtained. The single-particle spectrum at half-filling is in accord with the recent angle-resolved photoemission spectrum in the 1D cuprate SrCuO 2 and is in strong contrast with that in the 2D one Sr 2CuO 2Cl 2. In 2D, the behaviors of these excitation spectra are strongly dependent on electron concentration. Far away from half-filling, the single-particle spectrum includes both spin and charge excitations as expected in a Fermi liquid. On the other hand, near half-filling, the spectra are rather similar to those in 1D, indicating that the spin and charge degrees of freedom obey the different dynamics. The spectra in a two-leg ladder are similar to those in 2D.