Magnetic-impurity-induced modifications to ultrafast carrier dynamics in the ferromagnetic topological insulators Sb2-xVxTe3
Magnetic-impurity-induced modifications to ultrafast carrier dynamics in the ferromagnetic topological insulators Sb2-xVxTe3
复制标题
DOI：
10.1088/1367-2630/ab3ac6
复制
发表时间：
2019-09-04
影响因子：
3.3
通讯作者：
Kimura, A.
中科院分区：
文献类型：
--
作者：
Sumida, K.;Kakoki, M.;Kimura, A.
量子反常霍尔效应（QAHE）由于在无外磁场情况下具有无耗散的自旋极化和量子化电流，是低功耗器件应用的关键现象。然而，量子反常霍尔效应所记录的工作温度仍然很低。在此，我们从磁性、结构和电子特性以及超快载流子动力学的角度，对一系列组成为\(Sb_{2 - x}V_{x}Te_{3}\)（\(x = 0\)、\(0.015\)和\(0.03\)）的钒掺杂\(Sb_{2}Te_{3}\)样品中磁性掺杂剂引起的变化进行了系统研究。元素特异性的X射线磁圆二色性表明，钒掺杂\(Sb_{2}Te_{3}\)的铁磁性由主体载流子和磁性掺杂剂之间的\(p - d\)杂化所控制。用中红外脉冲激发的时间和角度分辨光电子能谱显示，拓扑表面态（TSS）下方由钒杂质诱导的态增加了散射通道，这将瞬态表面电子的持续时间显著缩短至100飞秒量级。这与原始样品所报道的较长持续时间形成鲜明对比，尽管在磁性或非磁性情况下，拓扑表面态都位于主体的体能隙内。这意味着在主体材料的体能隙区域存在迁移率隙，这将有助于实现稳定的量子反常霍尔效应。我们的研究结果为低能耗器件应用的材料设计提供了思路。
Quantum anomalous Hall effect (QAHE) is a key phenomenon for low power-consumption device applications owing to its dissipationless spin-polarized and quantized current in the absence of an external magnetic field. However, the recorded working temperature of the QAHE is still very low. Here we systematically investigate the magnetic dopants induced modifications from the view points of magnetic, structural and electronic properties and the ultrafast carrier dynamics in a series of V-doped Sb2Te3 samples of composition Sb2-xVxTe3 with x = 0, 0.015 and 0.03. Element specific x-ray magnetic circular dichroism signifies that the ferromagnetism of V-doped Sb2Te3 is governed by the p-d hybridization between the host carrier and the magnetic dopant. Time- and angle-resolved photoemission spectroscopy excited with mid-infrared pulses has revealed that the V impurity induced states underlying the topological surface state (TSS) add scattering channels that significantly shorten the duration of transient surface electrons down to the 100 fs scale. This is in a sharp contrast to the prolonged duration reported for pristine samples though the TSS is located inside the bulk energy gap of the host in either magnetic or non-magnetic cases. It implies the presence of a mobility gap in the bulk energy gap region of the host material that would work toward the robust QAHE. Our findings shed light on the material design for low-energy-consuming device applications.