We solve exactly a multiband one-dimensional Jahn-Teller (JT) model with strong electron correlations using the Lieb-Wu Bethe ansatz equations. As well as the metallic undistorted phase, we find two JT distorted phases. The first is a conducting phase, in which most carriers sit on one chain with the remaining carriers distributed equally among the other chains. We suggest that this phase is what is observed at low temperatures in ${\mathrm{Yb}}_4{\mathrm{As}}_3$. In the second phase all the carriers sit on one chain. This phase becomes a Mott insulator when the chain is half filled. We also show that a mean-field treatment of the model is misleading and that an exact treatment of interactions is essential.

• Received 2 December 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.3386