Charge-density wave and one-dimensional electronic spectra in blue bronze: Incoherent solitons and spin-charge separation

We present high resolution angle resolved photoemission spectroscopy (ARPES) data for K0.3MoO3 (blue bronze) and propose a theoretical description of these results based primarily on electron-electron interactions. The observed Fermi surface, with two quasi-one-dimensional sheets, is consistent with a ladder material with a weak interladder coupling. Hence, we base our description on spectral properties of one-dimensional ladders. The marked broadening of the ARPES line shape, a significant fraction of an eV, is interpreted in terms of spin-charge separation. A high-energy feature, which is revealed in the spectra near the Fermi momentum thanks to improved energy resolution, is seen as a signature of a higher-energy bound state of soliton excitations on a ladder.