Charge order induced in an orbital density-wave state

TL;DR

This paper investigates how charge order is induced in an orbital density-wave state in layered manganites, revealing the interplay between orbital and charge ordering driven by Fermi-surface nesting and their temperature dependence.

Contribution

It demonstrates that charge order is induced by orbital order with a different wavevector, and clarifies the temperature evolution of these orders in layered manganites.

Findings

Charge order with wavevector (π, π) is induced by orbital order.

Orbital and charge order parameters develop as √(T_{CO}-T) and (T_{CO}-T).

Orbital order stabilizes the CE-type spin arrangement below T_{CE}.

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 $T_{CE} < T_{CO}$.