Polarized ARPES spectra of undoped cuprates

Abstract

The spectral density (SD) in the ARPES spectra of antiferromagnetic (AFM) dielectrics Sr2CuO2Cl2 and Ca2CuO2Cl2 along the principal symmetry directions of the Brillouin zone was studied by the generalized tight binding method. At the valence band top of these undoped cuprates in the AFM state, there is a pseudogap of magnetic nature with Es(k)∼0–0.4 eV between a virtual level and the valence band proper. The observed similarity of dispersion along the Γ-M and X-Y directions can be explained by the proximity of the 3B1g triplet and the Zhang-Rice singlet levels. The value of parity of the polarized ARPES spectra at the Γ, M, and X points calculated for the AFM phase of undoped cuprates with an allowance for the partial contributions is even. The conditions favoring observation of the partial contributions in polarized ARPES spectra are indicated. Due to the spin fluctuations, the virtual level acquires dispersion and possesses a small spectral weight. Probably, this level cannot be resolved on the background of the main quasi-particle peak as a result of the damping effects.