论文标题
SR $ _2 $ iro $ _4 $
Spin-orbit-enhanced magnetic surface second-harmonic generation in Sr$_2$IrO$_4$
论文作者
论文摘要
先前在SR $ _2 $ iro $ _4 $中报道了一个异常的光学第二谐波发电（SHG）信号，并归因于隐藏的奇数块磁状态。在这里，我们使用大量磁化率，磁场依赖性SHG旋转各向异性以及重叠的宽场SHG成像和原子力显微镜测量的组合研究了该SHG信号的来源。我们发现，异常的SHG信号表现出两倍的旋转对称性，这是与晶体学失真相关的平面磁场方向的函数。我们还显示了跟踪大量抗铁磁堆叠模式的步骤边缘的SHG信号的变化。尽管我们不排除SR $ _2 $ IRO $ _4 $中隐藏订单的存在，但我们的结果完全表明，父级SR $ _2 $ _2 $ iro $ _4 $中的异常SHG信号源自表面磁通诱导的电 - 二波尔进程，这是由强旋转孔构成的强旋转式旋转量增强的。
An anomalous optical second-harmonic generation (SHG) signal was previously reported in Sr$_2$IrO$_4$ and attributed to a hidden odd-parity bulk magnetic state. Here we investigate the origin of this SHG signal using a combination of bulk magnetic susceptibility, magnetic-field-dependent SHG rotational anisotropy, and overlapping wide-field SHG imaging and atomic force microscopy measurements. We find that the anomalous SHG signal exhibits a two-fold rotational symmetry as a function of in-plane magnetic field orientation that is associated with a crystallographic distortion. We also show a change in SHG signal across step edges that tracks the bulk antiferromagnetic stacking pattern. While we do not rule out the existence of hidden order in Sr$_2$IrO$_4$, our results altogether show that the anomalous SHG signal in parent Sr$_2$IrO$_4$ originates instead from a surface-magnetization-induced electric-dipole process that is enhanced by strong spin-orbit coupling.
