Positron annihilation in YBa"2Cu"3O"7"-"δ: A clearer picture - Manuel, A.A.; Barbiellini, B.; Gauthier, M.; Hoffmann, L.; Jarlborg, T.; Massidda, S.; Peter, M.; Sadowski, W.; Shukla, A.; Walker, E. (Elsevier)
We obtain remarkable agreement between 2D-ACAR measurements in YBa"2Cu"3O"7"-"δ and calculations by the FLAPW method: order of magnitude for the amplitude of the (3.5+/-1 %) 2D-ACAR anisotropy. Theoretical predictions of the two-photons momentum distribution were made using both the FLAPW and the LMTO technique; the FLAPW results came out to be closer to measurement. The sharpness of the Fermi surface is comparable with theoretical prediction. Estimations give a full width of the ridge of 1.6+/-0.2 mrad which is the value given by our LDA band structure calculations. Substitution of Cu with Al (T"c = 77 K) yield a nearly tetragonal signal with much less ridge contribution. Substitution with comparable amounts of Ni and Zn had much less influence on the 2D-ACAR picture: this seems to be due to the fact that Al goes into the chains, where positron density is large, while Ni and Zn are located into the layers.
http://linkinghub.elsevier.com/retrieve/pii/0022-3697(93)90172-N
Keywords: V; U