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二维拓扑绝缘体退相干效应研究

Two-dimensional dephasing effects in topological insulators

  • 摘要: 拓扑绝缘体是当前凝聚态物理研究的热点.退相干效应对该体系的影响的研究不仅有重要的理论意义,而且也是实现未来量子器件的不可或缺的前期工作.文章作者从理论上研究了退相干对二维拓扑绝缘体特别是量子自旋霍尔效应的影响.研究结果表明,作为量子自旋霍尔效应的标志的量子化纵向电阻平台对不破坏自旋记忆的退相干效应(普通退相干)不敏感,但却对破坏自旋记忆的退相干效应(自旋退相干)非常敏感.因此,该量子化平台只能在尺寸小于自旋退相干长度的介观样品中存在,从而解释了量子自旋霍尔效应实验中所观测到的结果(见Science ,20

     

    Abstract: Topological insulator is one of the most attractive areas in condensed matter physics in recent years.The study of the dephasing effect in such systems has important theoretical meanings and meanwhile,is inevitable for the realization of future quantum devices.In our studies of the influence of dephasing on the two-dimensional topological insulator,especially the quantum spin Hall effect,we find that the quantized longitudinal resistance plateaus are robust against normal dephasing but fragile to spin dephasing. Thus, these quantized plateaus can only survive in mesoscopic samples in which the spin coherence length is smaller than the sample size. Our results are in excellent agreement with experiments (Science,2007,318:766). In addition, we define a new spin Hall resistance that also exhibits quantum plateaus, which are robust against both normal and spin dephasings. These novel quantum plateaus can thus survive in macroscopic samples and better reflect the topological nature of the quantum spin Hall effect.

     

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