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Imaging work and dissipation in the quantum Hall state in graphene

机译：石墨烯在量子霍尔态下的成像功和耗散

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摘要

Topology is a powerful recent concept asserting that quantum states could be globally protected against local perturbations(1,2). Dissipationless topologically protected states are therefore of major fundamental interest as well as of practical importance in metrology and quantum information technology. Although topological protection can be robust theoretically, in realistic devices it is often susceptible to various dissipative mechanisms, which are difficult to study directly because of their microscopic origins. Here we use scanning nanothermometry(3) to visualize and investigate the microscopic mechanisms that undermine dissipationless transport in the quantum Hall state in graphene. Simultaneous nanoscale thermal and scanning gate microscopy shows that the dissipation is governed by crosstalk between counterpropagating pairs of downstream and upstream channels that appear at graphene boundaries as a result of edge reconstruction. Instead of local Joule heating, however, the dissipation mechanism comprises two distinct and spatially separated processes. The work-generating process that we image directly, which involves elastic tunnelling of charge carriers between the quantum channels, determines the transport properties but does not generate local heat. By contrast, the heat and entropy generation process-which we visualize independently-occurs nonlocally upon resonant inelastic scattering from single atomic defects at graphene edges, and does not affect transport. Our findings provide an insight into the mechanisms that conceal the true topological protection, and suggest routes towards engineering more robust quantum states for device applications.
机译：拓扑学是一个有力的最新概念，它声称可以对量子态进行全局保护以防止局部扰动（1,2）。因此，无耗散的拓扑保护状态在计量学和量子信息技术中具有重大的基本意义和实际意义。尽管拓扑保护在理论上是可靠的，但在实际设备中，拓扑保护通常易受各种耗散机制的影响，由于其微观起源，因此很难直接进行研究。在这里，我们使用扫描纳米温度计（3）来可视化并研究破坏石墨烯中量子霍尔态中无耗散传输的微观机制。同时进行的纳米级热扫描和扫描门显微镜显示，耗散受边缘重构的结果在石墨烯边界处出现的反向传播的下游通道对和上游通道之间的串扰控制。但是，代替局部焦耳加热，耗散机制包括两个截然不同且在空间上分开的过程。我们直接成像的产生工作的过程涉及到量子通道之间电荷载流子的弹性隧穿，它决定了传输性质，但不会产生局部热量。相比之下，我们独立地观察到的热量和熵的生成过程非局部地发生在石墨烯边缘的单个原子缺陷共振非弹性散射时，并且不影响传输。我们的发现提供了对隐藏真正拓扑保护的机制的见解，并提出了为设备应用设计更健壮的量子态的途径。

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  • 来源
    《Nature》 |2019年第7784期|628-633|共6页
  • 作者

    Marguerite A.; Birkbeck J.; Aharon-Steinberg A.; Halbertal D.; Bagani K.; Marcus I.; Myasoedov Y.; Geim A. K.; Perello D. J.; Zeldov E.;

  • 作者单位

    Weizmann Inst Sci Dept Condensed Matter Phys Rehovot Israel;

    Univ Manchester Natl Graphene Inst Manchester Lancs England|Univ Manchester Sch Phys & Astron Manchester Lancs England;

    Weizmann Inst Sci Dept Condensed Matter Phys Rehovot Israel|Columbia Univ Dept Phys 538 W 120th St New York NY 10027 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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