Angle-resolved photoemission study of cobalt oxide superconductor NaxCoO2.yH2O : Observation of the Fermi surface

Abstract

Cobalt oxide superconductor NaxCoO2.yH2O is studied by angle-resolved photoemission spectroscopy (ARPES). We report the Fermi surface (FS) topology and electronic structure near the Fermi level (EF) of NaxCoO2.yH2O. Our result indicates the presence of the hexagonal FS centered at G point, while the small pocket FSs along G-K direction are absent similar to NaxCoO2. The top of the eg' band, which is expected in band calculations to form the small pocket FSs, extends to within 20 - 50 meV below EF, more closer to EF than in NaxCoO2. We discuss its possible role in superconductivity, comparing with other experimental and theoretical results.

15 pages, 3 figures

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• Is there a common theme behind the correlated-electron superconductivity in organic charge-transfer solids, cobaltates, spinels and fullerides?
• Identifying the pairing symmetry in sodium cobalt oxide by Andreev edge states
• Tuning Co valence state in cobalt oxyhydrate superconductor by post reduction
• Band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2: Fluctuation exchange study based on a single band model
• One-particle spectral properties of the t-J-$V$ model on the triangular lattice near charge order
• Evolution of electron Fermi surface with doping in cobaltates
• Similarities in electronic properties of organic charge-transfer solids and layered cobaltates