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TT: Tiefe Temperaturen

TT 12: Correlated Electrons: Low-dimensional Systems - Models

TT 12.8: Vortrag

Dienstag, 28. März 2006, 11:30–11:45, HSZ 304

Charge Response in Quasi-1D Wigner Lattice Systems — •Anup Mishra1, Matthias Mayr2, and Peter Horsch11Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany. — 2Dept. of Physics, Univ. of Tennesse, Knoxville, USA

Doped edge-sharing Cu-O chain compounds are ideal realizations of 1D Wigner lattices(WL). Such chains are found in the recently synthesized Na3Cu2O4 and Na8Cu5O10 systems [1] and are also structural elements in the composite compound Sr14−xCaxCu24O41. As a result of the structure the hopping matrix elements tl and hence the kinetic energy are small compared to the Coulomb energy. At low temperature the charge order resulting from Coulomb interaction VlV/l generates modulated Heisenberg chains with varying distance between spins. We discuss the charge dynamics of WL starting from a model of spinless fermions. We give a detailed discussion of domain-wall excitation spectra and excitonic states at doping x=1/2. In the model with t1 only the resulting periodicity of WL charge modulation may also be explained by a 4kF charge-density wave(CDW) arising from a Fermi surface instability. However due to the ≈ 90 Cu-O-Cu bond angle in edge-sharing chains |t2|>|t1|. Presence of t2 does not affect the classical WL order, but it changes the Fermi surface topology. This allows to distinguish the WL from the CDW on the basis of the modulation period. We present a detailed phase diagram taking into account t1, t2 and Vl. [1] P. Horsch, M. Sofin, M. Mayr, and M. Jansen, Phys. Rev. Lett. 94, 076403 (2005).

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