Non-trivial order parameter in Sr₂IrO₄

الأصل · EN

Electronic structure calculations obtained with an approach with density functional theory with an enhanced local Coulomb interaction, DFT+U, are presented for the relativistic magnetic insulator Sr₂IrO₄. The results are in accordance with experiments with a band gap and a small moment anti-ferromagnetic ground state. This solution is thereafter thoroughly analyzed in terms of Landau theory where it is found that the ordered magnetic moments only form a secondary order parameter while the primary order parameter is a higher order magnetic multipole of rank five. It is further observed that the electronic structure in the presence of this order parameter is related to the earlier proposed jₑff=1/2 model, but in contrast to that model the present picture can naturally explain the small magnitude of the ordered magnetic moments.