Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 18: Correlated Electrons: Low-dimensional Systems - Materials 2

TT 18.10: Vortrag

Dienstag, 26. Februar 2008, 17:45–18:00, H 2053

Electric field gradients in low dimensional cuprates - a comparative study — •Katrin Koch¹, Klaus Koepernik^1,2, and Helge Rosner¹ — ¹MPI-CPFS, Dresden — ²IFW, Dresden

The theoretical description of strongly correlated systems is still a challenging task. A possible approach to this problem resulting in realistic electron densities is the LSDA+U method where the strong Coulomb repulsion U is treated in a mean field like approximation. Unfortunately the parameter U is not known and needs to be evaluated, i.e. in comparison of calculated properties and experimental measurements.

Here, we present calculations for the electric field gradients (V_zz) on the Cu²⁺ sites in strongly correlated low dimensional cuprates. By comparing the calculated V_zz(U) with the V_zz from NMR experiments for these compounds we can evaluate U. To avoid numerical ambiguity we used two different DFT-band structure schemes: FPLO and WIEN2k. The results are consistent with respect to each other: In part we find good agreement with resulting values of U from other evaluation procedures, especially for strongly distorted Cu²⁺ environment (e.g. Cu₂P₂O₆CH₂), though considerable deviation in direction of smaller U values for other compounds (e.g. La₂CuO₄) is obtained. Possible causes for this deviation will be discussed.