Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 32: Correlated Electrons - Low-dimensional Materials II

TT 32.7: Vortrag

Dienstag, 8. März 2005, 17:45–18:00, TU H2053

Spin chains in (Ca,La,Sr)₁₄Cu₂₄O₄₁ — •Cosima Schuster and Udo Schwingenschlögl — Institut für Physik, Universität Augsburg

The (Ca,La,Sr)₁₄Cu₂₄O₄₁ compounds contain two different structural components, CuO₂ ladders and CuO chains. The compounds are intrinsically doped, whereby the main part of the holes can be assigned to the chains. The spin and charge order on the chains are strongly doping dependent and range from spin dimers over 3D antiferromagnetic order to ferromagnetic order in the La rich compounds. On the basis of the crystal structure we try to form a model for the chains on the basis of the Hubbard model. We choose the Hubbard model, because it is particle-hole-symmetric, and the doping is numerically easy to implement. In addition we study periodic potentials with different period. We examine, which potential is energetically favored and which charge and spin order is linked with this potential. In our investigations we concentrate on the quarter filled band. We find that a 2k_F periodic magnetic field leads – with interaction – to the highest energy gain but it is related with a large spin gap. On the other hand a 4k_F periodic potential is favored for strong interaction. In this case, we find no spin gap but a 2k_F oscillation of the magnetization. The difference to a Heisenberg chain is pointed out.