Spin waves and stability of zigzag order in the Hubbard model with spin-dependent hopping terms: Application to the honeycomb lattice compounds Na2IrO3 and α-RuCl3

摘要

Spin waves in the zigzag ordered antiferromagnetic state on a honeycomblattice are investigated within a Hubbard model with spin-dependent hoppingterms. Roles of the emergent Kitaev, Heisenberg, Dzyaloshinskii-Moriya, andsymmetric-off-diagonal spin interactions are investigated on the stability ofthe zigzag order. While the DM interactions are found to strongly destabilizethe zigzag order, the secondary spin-dependent hopping terms (associated withstructural distortions) are shown to strongly stabilize the zigzag order andaccount for magnetocrystalline anisotropy, easy axis, and spin wave gap. Thecalculated spin wave dispersion and energy scale are in good agreement withinelastic neutron scattering measurements on $m lpha - RuCl_3$ and $mNa_2 Ir O_3$.