Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
Nano Lett. 2010 Mar 10;10(3):1076-81. doi: 10.1021/nl100146n.
A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surface-to-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than approximately 2%, low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics.
一个简单的表面能带结构和一个大的体带隙使 Bi2Se3 成为新发现的三维拓扑绝缘体的参考材料，这些拓扑绝缘体表现出拓扑保护的传导表面态，位于体带隙内。在纳米结构中研究拓扑绝缘体，如 Bi2Se3，是有利的，因为高的比表面积可以增强表面态的影响；我们最近报道的一些拓扑绝缘体纳米带中的 Aharonov-Bohm 振荡就是一个很好的例子。理论上，通过打破时间反转对称性，在拓扑绝缘体中引入磁性杂质被预测会在表面态中打开一个小的能隙。在这里，我们通过使用磁性金属薄膜作为催化剂的气-液-固生长法，合成了磁性掺杂 Bi2Se3 纳米带。尽管掺杂浓度小于约 2%，但 Fe 掺杂 Bi2Se3 纳米带器件的低温输运测量在 30 K 以下显示出明显的 Kondo 效应，证实了磁性杂质存在于 Bi2Se3 纳米带中。磁性掺杂拓扑绝缘体纳米结构的能力为自旋电子学开辟了令人兴奋的机会。
