Dynamical properties of honeycomb-lattice magnets Na$_{2}$IrO$_{3}$

We studied dynamical properties of magnetic effective models for Na$_{2}$IrO$_{3}$. The effective magnetic models have been much discussed to explain the zigzag magnetic ordering of this compound [1-6]. The most characteristic point of the proposed models is that the presence of the Kitaev type anisotropy is expected in addition to the Heisenberg coupling. Although there are several proposals for the coupling magnitude of the effective models, the qualitative and quantitative evaluations have been still lacking from the viewpoint of dynamics. From the above background, we carried out numerical exact diagonalization and calculated the dynamical structure factors for the proposals in pioneering works [2,3,5,6]. The obtained results were compared with inelastic-neutron-scattering measurements [2]. We found that the parameter set proposed in ref. [6] well explains a characteristic boundary structure of the lowest excitation around Y point and an intensity distribution in the low energy region [2]. \\[4pt] [1] F. Ye, et al., Phys. Rev. B 85, 180403(R) (2012).\\[0pt] [2] S. K. Choi, et al., Phys. Rev. Lett. 1008, 127204 (2012).\\[0pt] [3] J. Chaloupka, G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 105, 027204 (2010); Phys. Rev. Lett. 110, 097204 (2013).\\[0pt] [4] I. Kimchi and Y. Z. You, Phys. Rev. B 84, 180407(R) (2011).\\[0pt] [5] V. M. Katukuri, et al., New J. Phys. 16, 013056 (2014).\\[0pt] [6] Y. Yamaji et al., Phys. Rev. Lett. 113, 107201 (2014).