Direct Fermi-Surface Image Of Hidden Nesting For Namo6o17 And Kmo6o17

We report direct Fermi-surface images obtained with angle-resolved photoemission spectroscopy (ARPES) for NaMo6O17 and KMo6O17 above the charge-density wave transition temperatures. We also report ARPES spectra of the valence band of NaMo6O17. The images imply a Fermi surface (FS) based on three underlying quasi-one-dimensional (quasi-1D) surfaces. Thus it agrees in detail with that expected in the hidden nesting picture of Whangbo et al. [Science 252, 96 (1991)], but differs greatly from a FS deduced in a previous study by Breuer et al. [Phys. Rev. Lett. 76, 3172 (1996)], which found only two underlying quasi-1D surfaces.