Abstract
We examine a Peierls ground state and its competing metastable state in the one-dimensional quarter-filled Peierls–Hubbard model with the nearest-neighbor repulsive interaction V and the electron–phonon interaction (∝1⁄K with K being the elastic constant). From the mean-field approach, we obtain the phase diagram for the ground state on the plane of parameters V and K. The coexistent state of the spin-density wave and the charge ordering is realized for large V and K. With decreasing K, it exhibits a first-order phase transition to the unconventional Peierls state which is described by the bond-centered charge-density-wave state. In the large region of the Peierls ground state in the phase diagram, there exists the metastable state where the energy takes a local minimum with respect to the lattice distortion. On the basis of the present calculation, we discuss the photoinduced phase observed in the (EDO-TTF)2PF6 compound.
