Qinlong Luo, Andrew Nicholson, Julián Rincón, Shuhua Liang, José Riera, Gonzalo Alvarez, Adriana Moreo, Elbio Dagotto
Recent experiments addressing the magnetic state of the two-leg ladder BaFe$_2$Se$_3$ compound unveiled a dominant spin arrangement involving ferromagnetically ordered 2$\times$2 Fe-superblocks, antiferromagnetically coupled among them. Using the electronic five-orbital Hubbard model and the real-space Hartree-Fock approximation, it is shown that this exotic state is indeed stable at electronic density $n$$\sim$6.0. A state close in energy with wavevector $(\pi,0)$ ($x$ = long ladder direction) becomes stable at $n$$\sim$5.5, as also found in KFe$_2$Se$_3$. The present study unveils several competing magnetic phases that could be experimentally stabilized varying $n$ or the electronic bandwidth. Similar results were obtained using two-orbital models, studied via Lanczos and DMRG techniques.
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http://arxiv.org/abs/1205.3239
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