Angle-resolved photoemission spectroscopy study on the Fermi surface topology ofNaxCoO2

Abstract

We report a systematic study onNaxCoO2 (0.3≤x≤0.72) using angle-resolved photoemission spectroscopy (ARPES), with a focuson the Fermi surface topology of the metallic samples. Within this dopingrange, we observed only one large hexagonal Fermi surface around theΓ-point, whichcomes from the a1g band. Contrary to most band calculations, our results show that theeg′ bandsnever cross the Fermi level to form small Fermi surface pockets near the K-point. The enclosed area ofthe a1g Fermi surface is found to be consistent with the Luttinger theoremwithin the doping range in this study. We also found that, atx = 1/3, the Fermi surface coincides with the zone boundary of the commensurate ordering, indicating the importance of charge fluctuations in this material.