Abstract
Reflectance spectra of polypyrrole (PPy) doped with obtained at 250 K and below, show the formation of a peak in the joint density of states at 110 and an associated redistribution of oscillator strength. In addition, a Fano-like resonance is observed at 70 . We discuss the results in terms of a transition to a density-wave ground state characterized by an energy gap and a pinned collective mode (at 70 ). Despite the energy gap, remains “metallic” at low temperatures; i.e., the gap spans only a part of the Fermi surface.
- Received 23 August 1999
DOI:https://doi.org/10.1103/PhysRevB.61.1635
©2000 American Physical Society