Polarized ARPES spectra of undoped cuprates

The spectral density (SD) in the ARPES spectra of anti ferromagnetic (AFM) dielectrics Sr2CuO2Cl2 and Ca2CuO2Cl2 along the principal symmetry directio ns of the Brillouin zone was studied by the generalized tight binding metho d. At the valence band top of these undoped cuprates in the AFM state, ther e is a pseudogap of magnetic nature with E-s(k) similar to 0-0.4 eV between a virtual level and the valence band proper. The observed similarity of di spersion along the Gamma -M and X-Y directions can be explained by the prox imity of the B-3(1g) triplet and the Zhang-Rice singlet levels. The value o f parity of the polarized ARPES spectra at the Gamma, M, and X points calcu lated for the AFM phase of undoped cuprates with an allowance for the parti al contributions is even. The conditions favoring observation of the partia l contributions in polarized ARPES spectra are indicated. Due to the spin f luctuations, the virtual level acquires dispersion and possesses a small sp ectral weight. Probably, this level cannot be resolved on the background of the main quasi-particle peak as a result of the damping effects. (C) 2001 MAIK "Nauka/Interperiodica".