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Competing Ground States in a Two-Band Model with on-site electron-phonon coupling

We study the ground state phase diagram of the two band discrete tight-binding model for MX chains. We include PPP-like Coulomb correlations and focus on the long- period/period-4 phase competition. The long period phase is driven by the on-site electron-phonon coupling and oc- curs for certain parameters even at commensurate filling, where the commensurate (Peierls- distorted) phase would normally be expected. We discuss the nature of this long-period phase and its relation to twinning and commensurate/incommensurate phase transitions.

Competing Ground States, Two-Band Model

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