论文标题
拓扑绝缘子薄膜中掺杂剂浓度诱导的磁交换相互作用的演变
Evolution of Dopant-Concentration-Induced Magnetic Exchange Interaction in Topological Insulator Thin Films
论文作者
论文摘要
可以通过将磁离子掺入拓扑绝缘子（TI）膜结合使用量子异常霍尔（QAH）效应的两种必不可少的成分，即拓扑和磁性。通过这种方法，QAH效应已在铬（CR） - 和/或钒（V）掺杂的Ti（BI，SB）2TE3薄膜中实现。在这项工作中，我们使用分子束外延（MBE）合成具有控制掺杂剂浓度的V-和CR掺杂的BI2TE3薄膜。通过执行磁通型传输测量，我们发现两个系统在磁掺杂剂浓度方面均显示出异常但相似的铁磁反应，具体来说，居里温度并未单调地增加，但在关键的掺杂剂浓度下显示了局部最大值。我们的角度分辨光发射光谱（ARPES）测量表明，CR/V掺杂将孔载体引入BI2TE3，因此将化学电位移向电荷中性点。此外，CR/V掺杂还减少了BI2TE3的自旋轨道耦合，该耦合将其从非平凡的Ti驱动到琐碎的半导体。 The unusual ferromagnetic response observed in Cr/V-doped Bi2Te3 thin films is attributed to the dopant-concentration-induced magnetic exchange interaction, which displays the evolution from the van Vleck-type ferromagnetism in a nontrivial magnetic TI to the Ruderman-Kittel-Kasuya-Yosida (RKKY)-type ferromagnetism in a微不足道的稀释磁性半导体。我们的工作提供了对磁掺杂的Ti薄膜的铁磁特性的见解，并促进了追求高温QAH效应。
Two essential ingredients for the quantum anomalous Hall (QAH) effect, i.e. topological and magnetic orders, can be combined by doping magnetic ions into a topological insulator (TI) film. Through this approach, the QAH effect has been realized in chromium (Cr)- and/or vanadium (V)-doped TI (Bi,Sb)2Te3 thin films. In this work, we synthesize both V- and Cr-doped Bi2Te3 thin films with controlled dopant concentration using molecular beam epitaxy (MBE). By performing magneto-transport measurements, we find that both systems show an unusual but yet similar ferromagnetic response with respect to magnetic dopant concentration, specifically the Curie temperature does not increase monotonically but shows a local maximum at a critical dopant concentration. Our angle-resolved photoemission spectroscopy (ARPES) measurements show that the Cr/V doping introduces hole carriers into Bi2Te3, which consequently move the chemical potential toward the charge neutral point. In addition, the Cr/V doping also reduces the spin-orbit coupling of Bi2Te3 which drives it from a nontrivial TI to a trivial semiconductor. The unusual ferromagnetic response observed in Cr/V-doped Bi2Te3 thin films is attributed to the dopant-concentration-induced magnetic exchange interaction, which displays the evolution from the van Vleck-type ferromagnetism in a nontrivial magnetic TI to the Ruderman-Kittel-Kasuya-Yosida (RKKY)-type ferromagnetism in a trivial diluted magnetic semiconductor. Our work provides insights into the ferromagnetic properties of magnetically doped TI thin films and facilitates the pursuit of high-temperature QAH effect.
