Reentrant Charge Order Transition in the Extended Hubbard Model

Abstract

We study the extended Hubbard model with both on-site and nearest neighbor Coulomb repulsion ( $U$ and $V$, respectively) in the dynamical mean field theory. At quarter filling, the model shows a transition to a charge ordered phase with different sublattice occupancies ${n}_{\mathrm{A}}\ensuremath{\ne}{n}_{\mathrm{B}}$. The effective mass increases drastically at the critical $V$ and a pseudogap opens in the single-particle spectral function for higher values of $V$. The ${V}_{\mathrm{c}}(T)$ curve has a negative slope for small temperatures, i.e., the charge ordering transition can be driven by increasing the temperature. This is due to the higher spin entropy of the charge ordered phase.