Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 19: Correlated Electrons: Low-dimensional Materials

TT 19.13: Vortrag

Dienstag, 28. März 2006, 17:15–17:30, HSZ 301

Density Functional Calculations of the Total Energy and Electronic Structure of Na_xCoO₂ Using the LDA — •Klaus Koepernik, Helmut Eschrig, Jochen Geck, and Bernd Buechner — IFW Dresden, Germany

We analyze the low temperature electronic structure of Na_0.75CoO₂. Full potential all-electron density functional calculations within the local density approximation (LDA) have been performed. A number of low symmetry superstructures in the Sodium planes have been compared with respect to the LDA total energy. Our findings support the symmetry recently found in diffraction experiments. The superstructure favoured by LDA calculations shows a Sodium charge density wave (CDW) in aggreement with the experimental results. Besides Coulomb energy arguments in favour of the CDW the density of states indicates a band energy gain due to the CDW. The band energy favorization of the CDW is further supported by a small Sodium offset from its symmetry position, increasing the amplitude of the wave. Comparision with the cuprates shows rather big differences in the doping mechanism and therefore in the low energy physics.