We use resonant inelastic x-ray scattering (RIXS) at the Ir $L_3$ edge to study the effect of hole doping upon the $J_{\text{eff}}=\frac{1}{2}$ Mott-insulating state in ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$, via Rh replacement of the Ir site. The spin-wave gap, associated with XY-type spin-exchange anisotropy, collapses with increasing Rh content, prior to the suppression of the Mott-insulating state and in contrast to electron doping via La substitution of the Sr site. At the same time, despite heavy damping, the $d-d$ excitation spectra retain their overall amplitude and dispersion character. A careful study of the spin-wave spectrum reveals that deviations from the $J_1-J_2-J_3$ Heisenberg used to model the pristine system disappear at intermediate doping levels. These findings are interpreted in terms of a modulation of Ir-Ir correlations due to the influence of Rh impurities upon nearby Ir wave functions, even as the single-band $J_{\text{eff}}=\frac{1}{2}$ model remains valid up to full carrier delocalization. They underline the importance of the transition metal site symmetry when doping pseudospin systems such as ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$.

中文翻译：

---

Rh掺杂的Sr2IrO4中的自旋波隙塌陷

我们在Ir处使用共振非弹性X射线散射（RIXS） ${\mathrm{大号}}_3$ 边缘研究空穴掺杂对 ${Ĵ}_{\text{效}}=\frac{\mathrm{1个}}{2}$ 处于莫特绝缘状态 $r_2{\mathrm{氧化铁}}_4$，通过Ir站点的Rh替换。与XY型自旋交换各向异性相关的自旋波间隙在抑制Mott绝缘状态之前与Rh含量增加而崩溃，这与通过Sr位点的La取代进行电子掺杂相反。同时，尽管阻尼很大，$d-d$激发光谱保持其整体振幅和色散特性。对自旋波谱进行仔细研究后发现，与自旋波谱的偏差${Ĵ}_{\mathrm{1个}}-{Ĵ}_2-{Ĵ}_3$海森堡过去用来模拟原始系统在中等掺杂水平下消失的现象。这些发现可以通过对Ir-Ir相关性的调制来解释，这是由于Rh杂质对附近的Ir波函数（甚至是单波段）的影响${Ĵ}_{\text{效}}=\frac{\mathrm{1个}}{2}$该模型在整个运营商去本地化之前一直有效。他们强调了在掺杂伪自旋系统时，过渡金属位点对称的重要性，例如$r_2{\mathrm{氧化铁}}_4$。