Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7, Canada.
CMP&MS Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
Phys Rev Lett. 2013 Feb 15;110(7):076402. doi: 10.1103/PhysRevLett.110.076402. Epub 2013 Feb 13.
The electronic structure of the honeycomb lattice iridates Na(2)IrO(3) and Li(2)IrO(3) has been investigated using resonant inelastic x-ray scattering (RIXS). Crystal-field-split d-d excitations are resolved in the high-resolution RIXS spectra. In particular, the splitting due to noncubic crystal fields, derived from the splitting of j(eff)=3/2 states, is much smaller than the typical spin-orbit energy scale in iridates, validating the applicability of j(eff) physics in A(2)IrO(3). We also find excitonic enhancement of the particle-hole excitation gap around 0.4 eV, indicating that the nearest-neighbor Coulomb interaction could be large. These findings suggest that both Na(2)IrO(3) and Li(2)IrO(3) can be described as spin-orbit Mott insulators, similar to the square lattice iridate Sr(2)IrO(4).
使用共振非弹性 X 射线散射（RIXS）研究了蜂窝状晶格铱酸盐 Na(2)IrO(3) 和 Li(2)IrO(3)的电子结构。在高分辨率 RIXS 光谱中可以分辨出晶场分裂的 d-d 激发。特别是，由于非立方晶场导致的分裂，源自 j(eff)=3/2 态的分裂，比典型的铱酸盐中的自旋轨道能量标度小得多，验证了 j(eff)物理在 A(2)IrO(3)中的适用性。我们还发现，在 0.4eV 左右存在粒子-空穴激发能隙的激子增强，表明最近邻库仑相互作用可能很大。这些发现表明，Na(2)IrO(3)和 Li(2)IrO(3)都可以被描述为自旋轨道莫特绝缘体，类似于方晶格铱酸盐 Sr(2)IrO(4)。
