Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 23: Posters Superconductivity, Solids at Low Temperature

TT 23.23: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU D

Strong spin triplet contribution of the first removal state in the insulating regime of Bi-cuprates — •R.-S. Unger¹, C. Janowitz¹, U. Seidel¹, A. Krapf¹, R. Manzke¹, V.A. Gavrichkov², and S.G. Ovchinnikov² — ¹Humboldt Universität zu Berlin, Institut für Physik, 12489 Berlin — ²L.V.Kirensky Institute of Physics of the Sibirian Branch of the Russian Academy of Science, Krasnoyarsk, 660036, Russia

The experimental dispersion of the first removal state in the insulating regime of Bi₂Sr₂Ca_1−xY_xCu₂O_8+δ is found to differ significantly from that of other parent materials: oxyclorides and La₂CuO₄. For Y-contents of 0.92≥x≥0.55 the crystal lattice parameters a,b,c change very strongly. This (a,b) parameter increase and c parameter decrease results in an unconventional three peak structure at (0,0);(π/2,π/2);(π,π) for x=0.92. We can describe the experimental data only beyond the framework of the 3-band pd-model involving the representations of a new triplet counterpart for the Zhang-Rice singlet state [1]. The former results, obtained on a cuprate with two CuO₂-layers per unit cell, is found to be universal. Measurements on single layered Bi₂Sr_2−xLa_xCu₂O_6+δ give similar results.

[1] JETP Lett, 80(11) in print. (2004)