Dirac-fermion-mediated ferromagnetism in a topological insulator
Dirac-fermion-mediated ferromagnetism in a topological insulator
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DOI：
10.1038/nphys2388
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发表时间：
2012-10-01
期刊：
影响因子：
19.6
通讯作者：
Tokura, Yoshinori
中科院分区：
文献类型：
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作者：
Checkelsky, Joseph G.;Ye, Jianting;Tokura, Yoshinori
拓扑绝缘子是一类新发现的材料，在体绝缘子(1-6)的表面上存在螺旋导电模式。最近，理论工作表明，在这些材料中，破坏规范对称性(7)或时间反转对称性(8)会产生奇特的状态，如果实现，这代表着朝着实现新的磁电效应(9，10)迈出了实质性的一步，以及对量子计算有用的工具(11)。在这里，我们证明了后一种对称性破缺是由于磁性杂质与狄拉克费米子(12，13)相互作用而产生的铁磁性。利用基于解理的掺锰Bi2Te3-ySey单晶的器件，应用固体-介电和离子-液体两种选通方法，我们可以测量磁性离子存在时，体禁带内表面态的输运响应。通过跟踪反常霍尔效应，我们发现表面模支持稳健的铁磁性和磁导，这与增强的一维边缘态在磁畴壁上的输运是一致的。对量子输运现象这一证据的观察表明，这些奇异的状态在设备中是可访问的，并可能有助于集中讨论提出的广泛方法，以实验实现量子反常霍尔效应(8，10)和量子计算所需的状态(14，15)。
Topological insulators are a newly discovered class of materials in which helical conducting modes exist on the surface of a bulk insulator(1-6). Recently, theoretical works have shown that breaking gauge symmetry(7) or time-reversal symmetry(8) in these materials produces exotic states that, if realized, represent substantial steps towards realizing new magnetoelectric effects(9,10) and tools useful for quantum computing(11). Here we demonstrate the latter symmetry breaking in the form of ferromagnetism arising from the interaction between magnetic impurities and the Dirac fermions(12,13). Using devices based on cleaved single crystals of Mn-doped Bi2Te3-ySey, the application of both solid-dielectric and ionic-liquid gating allows us to measure the transport response of the surface states within the bulk bandgap in the presence of magnetic ions. By tracking the anomalous Hall effect we find that the surface modes support robust ferromagnetism as well as magnetoconductance that is consistent with enhanced one-dimensional edge-state transport on the magnetic domain wall. Observation of this evidence for quantum transport phenomena demonstrates the accessibility of these exotics states in devices and may serve to focus the wide range of proposed methods for experimentally realizing the quantum anomalous Hall effect(8,10) and states required for quantum computing(14,15).