Robert Wallauer
Department of Physics, Technion - Israel Institute of Technology,
Haifa
We used Sr2CuO2Cl2 as a model system with antiferromagnetic order below 250 K and a well defined q-vector to measure the sensitivity of ARPES to the presence of short-range correlations. We observe in agreement with a tight-binding model and other ARPES measurements the maximum of the highest occupied band at the (pi/2,pi/2)-point with significant spectral weight beyond the antiferromagnetic zone boundary. By heating the sample up to 450 K, almost twice the Neel temperature, we observe almost no change in the spectrum. Inelastic neutron scattering experiments indicate a correlation length of around 20 lattice sites at this temperature. In order to achieve shorter correlation lengths we substitute spin 1/2-Cu2+-atoms by spinless Zn2+. By combining the ARPES data with NMR measurements we are able to relate the temperature and Zn-subsitution level to a correlation length and quantify the decrease of spectral weight beyond the (pi/2,pi/2)-point. Even at correlation lengths as low as three lattice sites we still observe a population of the back-bended band.