Study of Meta-stable States and Multiple Charge Orderings in La1/3Sr2/3FeO3 Using First-principles

La1/3Sr2/3FeO3 is a strongly correlated material exhibiting the strong interplay between spin, charge, and lattice degrees of freedom. It is an antiferromagnetic Mott insulator at low temperature below 200K accompanying a charge ordering with the Fe-O bond disproportionation. The charge ordering driven by magnetism shows the Fe3+/Fe5+/Fe3+ structure along the [111] direction and it disappears above 200K as the magnetic order is suppressed. Using first-principles calculations, we identify meta-stable states which can occur near the critical temperature. We compute the energy path along the meta-stable states using the nudged elastic band method and find multiple charge ordering states with competing energetics. Those multiple charge orders exhibit distinct structural distortions and the phase of charge order parameter is locked with the phase of spin order parameter. Our results can provide an insightful explanation to the slow dynamics of this material observed in the ultra-fast experimental measurement.