National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China.
Nanoscale. 2017 Aug 31;9(34):12372-12378. doi: 10.1039/c7nr02807e.
Time-reversal symmetry is broken by magnetic doping in topological insulators (TIs). An energy gap at the Dirac point opens and thus, generates numerous surface carriers. TI nanostructures are an ideal platform to investigate exotic surface transport behavior due to their large surface-to-volume ratio, which enhances the contribution of the TI surface states. However, magnetic doping into TI nanostructures has been challenging, and induced magnetic behavior has remained elusive. Herein, we have synthesized Fe-doped BiSe nanowires using a facile chemical vapor deposition with a doping concentration of ∼1 at%. The combined structural characterizations illustrate the homogeneous distribution of the Fe dopants. Cryogenic magnetic force microscopy gives direct evidence of the spontaneous magnetization with a Curie temperature of ∼40 K in a single nanowire. The transport measurements show a quantum transition from weak anti-localization to weak localization behavior. All the evidence indicates the existence of intrinsic ferromagnetism and gapped topological surface states in the TI nanowires, paving a way for future memory and magnetoelectric nanodevice applications.
在拓扑绝缘体（TI）中，时间反转对称性被磁场掺杂所破坏。在狄拉克点处出现能隙，从而产生大量的表面载流子。由于 TI 表面态的贡献较大，TI 纳米结构具有大的表面积与体积比，是研究奇异表面输运行为的理想平台。然而，将磁场掺杂到 TI 纳米结构中一直具有挑战性，并且诱导的磁性行为仍然难以捉摸。在此，我们使用简便的化学气相沉积法，在 BiSe 纳米线中合成了掺杂浓度约为 1 at%的 Fe 掺杂剂。综合结构表征说明了 Fe 掺杂剂的均匀分布。低温磁力显微镜直接给出了在单个纳米线中具有约 40 K 居里温度的自发磁化的证据。输运测量表明从弱反局域到弱局域行为的量子转变。所有证据表明 TI 纳米线中存在本征铁磁性和带隙拓扑表面态，为未来的记忆和磁电纳米器件应用铺平了道路。
