Spin-orbital state induced by strong spin-orbit coupling

強いスピン軌道相互作用によって誘起されるスピン軌道状態

大西 弘明  

Onishi, Hiroaki

To clarify a crucial role of a spin-orbit coupling in the emergence of novel spin-orbital states in a -electron compound SrIrO, we study ground state properties of a -orbital Hubbard model on a square lattice by Lanczos diagonalization. In the absence of the spin-orbit coupling, the ground state is spin singlet when the Hund's rule coupling is small, while the ground state turns to be a fully polarized ferromagnetic state with the increase of the Hund's rule coupling. On the other hand, when we include the strong spin-orbit coupling, a ferromagnetic state appears even if the Hund's rule coupling is small. In the spin-orbit-induced ferromagnetic state, the total spin is reduced from the fully polarized one, since up-spin and down-spin states are mixed. Regarding the orbital state, we find the so-called complex orbital state, in which -orbital states are mixed with complex coefficients.