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Tunable interacting composite fermion phases in a half-filled bilayer-graphene Landau level

机译：半填充双层石墨烯朗道能级的可相互作用的复合费米子相

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Non-Abelian anyons are a type of quasiparticle with the potential to encode quantum information in topological qubits protected from decoherence(1). Experimental systems that are predicted to harbour non-Abelian anyons include p-wave superfluids, superconducting systems with strong spin-orbit coupling, and paired states of interacting composite fermions that emerge at even denominators in the fractional quantum Hall (FQH) regime. Although even-denominator FQH states have been observed in several two-dimensional systems(2-4), small energy gaps and limited tunability have stymied definitive experimental probes of their non-Abelian nature. Here we report the observation of robust even-denominator FQH phases at half-integer Landau-level filling in van der Waals heterostructures consisting of dual-gated, hexagonal-boron-nitride-encapsulated bilayer graphene. The measured energy gap is three times larger than observed previously(3,4). We compare these FQH phases with numerical and theoretical models while simultaneously controlling the carrier density, layer polarization and magnetic field, and find evidence for the paired Pfaffian phase(5) that is predicted to host non-Abelian anyons. Electric-field-controlled level crossings between states with different Landau-level indices reveal a cascade of FQH phase transitions, including a continuous phase transition between the even-denominator FQH state and a compressible composite fermion liquid. Our results establish graphene as a pristine and tunable experimental platform for studying the interplay between topology and quantum criticality, and for detecting non-Abelian qubits.
机译：非阿贝尔正离子是一种准粒子，具有在受退相干保护的拓扑量子位中编码量子信息的潜力（1）。预计将包含非阿贝尔原理的实验系统包括p波超流体，具有强自旋轨道耦合的超导系统以及相互作用的复合费米子的成对状态，它们在分数量子霍尔（FQH）体制的偶数分母处出现。尽管在几个二维系统中已观察到偶分母FQH状态（2-4），但小能隙和有限的可调谐性阻碍了非阿贝尔性质的确定性实验探针。在这里，我们报告了在范德华异质结构的半整数Landau级填充中由双门，六方硼氮化硼封装的双层石墨烯组成的稳健的偶分母FQH相的观察结果。测得的能隙是以前观察到的三倍（3,4）。我们将这些FQH相与数值模型和理论模型进行了比较，同时控制了载流子密度，层极化和磁场，并发现了成对的Pfaffian相（5）的证据，该Pfaffian相预计将承载非阿贝尔正离子。电场控制的具有不同Landau能级指数的状态之间的相交揭示了FQH相变级联，包括偶分母FQH状态和可压缩复合费米子液体之间的连续相变。我们的结果建立了石墨烯作为原始且可调谐的实验平台，用于研究拓扑与量子临界之间的相互作用以及检测非阿贝尔量子位。

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  • 来源
    《Nature》 |2017年第7672期|360-364|共5页
  • 作者

    Zibrov A. A.; Kometter C.; Zhou H.; Spanton E. M.; Taniguchi T.; Watanabe K.; Zaletel M. P.; Young A. F.;

  • 作者单位

    Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA;

    Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA;

    Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA;

    Univ Calif Santa Barbara, Calif Nanosyst Inst, Santa Barbara, CA 93106 USA;

    Natl Inst Mat Sci, Adv Mat Lab, Tsukuba, Ibaraki 3050044, Japan;

    Natl Inst Mat Sci, Adv Mat Lab, Tsukuba, Ibaraki 3050044, Japan;

    Princeton Univ, Dept Phys, Princeton, NJ 08544 USA;

    Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 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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