Charge order induced in an orbital density-wave state

Abstract

Motivated by the recent ARPES measurements (Evtushinsky et. al., PRL {\bf 105}, 147201 (2010)) and evidence for the density-wave state for the charge and orbital ordering (Garc\'{i}a et al., PRL {\bf 109}, 107202 (2012)) in La$_{0.5}$Sr$_{1.5}$MnO$_4$, the issue of charge and orbital ordering in a two orbital tight-binding model for layered manganite near half doping is revisited. We find that the charge order with an ordering wavevector 2${\bf Q}$ = $(\pi, \pi)$ is induced by the orbital order of $B_{1g}$ representation with a different ordering wavevector ${\bf Q}$, where the primary order parameter results from the strong Fermi-surface nesting. The orbital and charge order parameters develop according to $\sqrt{T_{CO}-T}$ and $T_{CO}-T$, respectively, by decreasing the temperature below the orbital ordering temperature $T_{CO}$. Moreover, the orbital order is found to stabilize the CE-type spin arrangement observed experimentally below $T_{CE} < T_{CO}$.