Abstract

We report angle-resolved photoemission spectra of η Mo4O11, a layered metal that undergoes two-charge density wave transitions at 109K and 30K. We have directly observed the "hidden one-dimensional " Fermi surface and an anisotropic gap opening associated with the 109K transition, in agreement with the band theoretical description of the CDW transition. In addition, as in other hidden 1D materials such as NaMo6O17, the ARPES line shapes show certain anomalies, which we discuss in terms of non-Fermi-liquid physics and possible roles of disorder. © 2005 The American Physical Society.