The electronic properties of the quasi-one-dimensional (1D) oxide conductor ${\mathrm{Li}}_{0.9}{\mathrm{Mo}}_6{\mathrm{O}}_{17}$ have been investigated using high-momentum and energy resolution photoelectron spectroscopy at temperatures above and below the metal-semiconductor transition temperature. Considerable spectral intensity at the Fermi energy $\left(E_F\right)$ is observed at room temperature, and a sharp feature corresponding to a band crossing $E_F$ is clearly resolved for states along the quasi-1D axis. Below the metal-semiconductor transition at 24 K, a gap is clearly observed to open at $E_F$. Our data do not support the assertion that the low energy excitations of electrons in ${\mathrm{Li}}_{0.9}{\mathrm{Mo}}_6{\mathrm{O}}_{17}$ should be described in a Luttinger liquid model.

• Received 16 April 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.1235