Anisotropic High Conductivity of delafossite PdCoO₂ Investigated by ARPES and Polarization-dependent XAS

Han-Jin Noh, Chonnam National University

Delafossite PdCoO₂ is an interesting oxide in that its in-plane electrical conductivity is higher than that of Pd metal, which is quite contrast to the general trend that metallic oxides have lower conductivity due to electron correlation effects. In order to understand the peculiar property, we investigated the electronic structure by using angle-resolved photoemission spectroscopy (ARPES), core level x-ray photoemission spectroscopy (XPS), and polarization-dependent x-ray absorption spectroscopy (XAS). The XAS spectra show the Co valence state and the orbital character of the conduction band of delafossite PdCoO₂. The XPS spectra reveal that the compound consist of correlated insulator layers and good metallic layers [1]. The ARPES spectra show that the bulk electronic structure is in a good agreement with the band calculation result by the LDA method. An explicit connection between the electronic structure and the anisotropic high conductivity has been established by ARPES [2,3]. By combining all the spectroscopic data, we provide a consistent picture on the origin of the good conductivity of the delafossite oxide.

References

[1] H.-J. Noh et al., Phys. Rev. B 80, 073104 (2009).

[2] H.-J. Noh et al., Phys. Rev. Lett. 102, 256404 (2009).

[3] K. Kyoo et al., Phys. Rev. B 80, 035116 (2009).