M. Ahsan Zeb, Hae-Young Kee
There has been a rapidly growing interest on the interplay between spin-orbit coupling (SOC) and Hubbard interaction U in correlated materials. A current consensus is that the stronger the SOC, the smaller is the critical interaction Uc required for a spin-orbit Mott insulator, because the atomic SOC is a local interaction leading to a narrower bandwidth. Contrary to this expectation, we find that, in orthorhombic perovskite oxides (Pbnm), the stronger the SOC, the bigger the Uc. This is originated from a line of Dirac node in Jeff=1/2 bands near the Fermi level inherited from a combination of the lattice structure and a large SOC. Due to this protected line of nodes, there are small hole and electron pockets in SrIrO3, and such a small density of states makes Hubbard interaction less efficient in building a magnetic insulator. The full phase diagram in U vs. SOC is obtained, where non-magnetic semimetal, magnetic metal, and magnetic insulator are found. Magnetic ordering patterns beyond Uc are also presented. We further discuss implications of our finding in relation to other perovskites such as SrRhO3 and SrRuO3.
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http://arxiv.org/abs/1206.5836
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