单晶金属Bi(111)膜中电荷与自旋的输运研究

项目名称： 单晶金属Bi(111)膜中电荷与自旋的输运研究

项目编号： No.10874217

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 电工技术

项目作者： 梁学锦

作者单位： 中国科学院物理研究所

项目金额： 39万元

中文摘要： 自旋－轨道相互作用（SOI）导致了许多新奇的量子效应，如金膜中的"巨"自旋霍尔效应（SHE），拓扑绝缘体预言和发现等，这些效应给自旋电子学和量子计算等研究带来了憧憬。外延制备的单晶Bi膜因具有很强的SOI效应，其输运特性便成为关注的热点。尽管历史上曾被广泛深入的研究，但由于制备技术的限制，Bi膜的输运性质一直悬而未决。本研究计划通过三年的努力，首先确定了大面积单晶Bi膜的外延制备工艺，发现了Bi膜的温度特性和磁输运特性，即单晶Bi膜中存在一个与厚度相关的特征温度，Tc：当温度T> Tc时材料是绝缘的，T< Tc时，材料是金属性的，Tc随膜厚增加而减小。平行磁场的输运测试表明较薄的膜中存在较强的反弱局域化效应（WAL），同样WAL也深刻影响着较薄的膜在垂直磁场中的输运特性－在零磁场附近正磁阻产生较大的变化。这些结果表明，Bi膜的表面附近存在很强的SOI效应，Bi膜的表面态是金属性的，当膜较薄时其输运特性取决于表面态。另一方面，上述结论也表明我们只可能在Tc以上通过输运测试"看到"由于量子尺寸效应导致的金属绝缘体相变，这个结论较好地解释了为什么40年来一直未观测到这个理论预言。

中文关键词： 自旋轨道相互作用;单晶Bi膜;特征温度;反弱局域化

英文摘要： Spin-orbit interaction (SOI) leads to many new striking quantum effect, such as a great spin Hall effect found in gold film at RT, topo-insulator predicted and discovered subsequently etc. which bring much hope to the studies in spintronics and solid state quantum calculation. There is very strong SOI effect in the epitaxial single crystal Bi film which results in focusing on its transport properties. Historically the transport properties of Bi film were studied widely for its strong quantum size effect inside, however, it remains unclear mainly because of the poor quality of film. In this research plan we spent 3 years studying the transport properties of epitaxial Bi film. Firstly we have obtained the techniques for growing large area flat Bi films. Secondly we measured the temperature and magnetic field dependences of Bi film and found there is a thickness dependent characteristic temperature, Tc. The higher the Tc is the thicker the film thickness. When T&gt;Tc the film is insulating, while T&lt;Tc it is metallic. The parallel magnetic field dependences of magnetic-resistance (MR) showed the thinner the film is the larger the weak anti-localization (WAL). The vertical magnetic field dependences of the MR indicate the larger slope for the thinner films due to stronger WAL in the thinner films. Those results showed there is very strong SOI effect at the surface or interface. The surface (interface) states are metallic which should originate from the SOI effect. When the film is thin enough the surface (interface) states dominate the film transport. Also it is showed the transition of semimetal to semiconductor (SMSC) due to quantum size effect (which was predicted 40 years ago) inside film only can be observed by transport when T&gt; Tc.

英文关键词： SOI; Single-crystal Bi film; characteristic temperature; weak anti-localization