Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 29: Correlated Electrons: Low-dimensional Systems - Materials 2
TT 29.11: Vortrag
Mittwoch, 25. März 2009, 17:00–17:15, HSZ 301
Anomalous dielectric response of the copper oxide chains in LiCuVO4. — •Yulia Matiks, Peter Horsch, Reinhard Kremer, Bernhard Keimer, and Alexander Boris — Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart
Spectroscopic ellipsometry has been used to investigate the low-lying electronic excitations in the strongly correlated chain copper oxide LiCuVO4 in the range 0.7 - 6.5 eV at temperatures 6 - 350 K. The Zhang-Rice singlet (ZRS) state has been evidenced in edge-sharing copper oxide chains for the first time. Temperature dependence of the ZRS peak identified in the dielectric response along the chains follows spin correlations within the chains that make ZRS apparent at 6 K but strongly suppressed and invisible at 300 K. This behavior is in a good agreement with recent cluster calculations within a pd-Hubbard model. [1] The integrated optical conductivity for polarization along the chains confirms the redistribution of the spectral weight between ZRS and non-bonding O2p states below 80 K. The corresponding effective number of charge carriers transferred between the states is 0.02 electrons per Cu atom indicating the kinetic energy gain of about 10 meV, which is of the same order of magnitude as the exchange integrals of the competing nearest J1 = -2.1 meV and next-nearest J2 = 4.3 meV neighbor interactions [2]. For polarization perpendicular to the chains, no spectral weight transfer between individual bands is observed.
[1] J. Málek et al., Phys. Rev. B 78, 060508 (R) (2008).
[2] M. Enderle et al., Europhys. Lett. 70, 237 (2005).