Theoretical study of thermoelectric and Hall effects in the layered cobalt oxides, image Original Research Article

We examine the response of the transport properties to the magnetic field and temperature gradient in the Hubbard model on the kagomé lattice within the limit of U→∞U→∞, using the “retraceable-path” approximation. The layered cobalt oxides, NaxCoO2NaxCoO2, involve the triangular lattice of the cobalt ions. However, the electron trajectory makes up the kagomé lattice due to the orbital degeneracy of t2gt2g states. It is shown that this kagomé lattice hidden in the CoO2 layer exhibits the anomalous high-temperature Hall effect recently observed by Wang et al.