Landau quantization and highly mobile fermions in an insulator
Landau quantization and highly mobile fermions in an insulator
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DOI：
10.1038/s41586-020-03084-9
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发表时间：
2020-10
期刊：
影响因子：
64.8
通讯作者：
Pengjie Wang;Guo Yu;Yanyu Jia;Michael Onyszczak;F. A. Cevallos;Shiming Lei;S. Klemenz;Kenji Watanabe;T. Taniguchi;R. Cava;L. Schoop;Sanfeng Wu
中科院分区：
文献类型：
--
作者：
Pengjie Wang;Guo Yu;Yanyu Jia;Michael Onyszczak;F. A. Cevallos;Shiming Lei;S. Klemenz;Kenji Watanabe;T. Taniguchi;R. Cava;L. Schoop;Sanfeng Wu
在强关联材料中，准粒子激发可以携带分数量子数。一个有趣的可能性是在绝缘体中形成分馏的、电荷中性的费米子--例如，自旋子和费米子激子--从而导致中性费米子表面和朗道量子化。虽然先前在量子自旋液体、拓扑近藤绝缘体和量子霍尔系统中的实验已经暗示了电荷中性的费米表面，但它们存在的证据仍然是不确定的。在这里，我们报告的实验观察到的朗道量子化的二维绝缘体，单层碲化钨（WTe 2），一个大的能隙拓扑绝缘体，。使用的检测方案，避免边缘的贡献，我们发现大的量子振荡材料的磁阻，与发病场小约0.5特斯拉。尽管电阻很大，但振荡曲线具有许多周期，模仿了金属中的Shubnikov-de哈斯振荡。在超低温下，观察到的振荡演变成1.6特斯拉附近的离散峰，以上的朗道量子化制度是充分发展。这种低起始场的量子化是可比的高迁移率的传统二维电子气的行为。我们的实验要求进一步调查的不寻常的基态的WTe 2单层，包括设备组件的影响和可能存在的移动的费米子和电荷中性的费米面内的绝缘间隙。
In strongly correlated materials, quasiparticle excitations can carry fractional quantum numbers. An intriguing possibility is the formation of fractionalized, charge-neutral fermions—for example, spinons and fermionic excitons,—that result in neutral Fermi surfaces and Landau quantization,in an insulator. Although previous experiments in quantum spin liquids, topological Kondo insulators, –and quantum Hall systems,have hinted at charge-neutral Fermi surfaces, evidence for their existence remains inconclusive. Here we report experimental observation of Landau quantization in a two-dimensional insulator, monolayer tungsten ditelluride (WTe2), a large-gap topological insulator, , –. Using a detection scheme that avoids edge contributions, we find large quantum oscillations in the material’s magnetoresistance, with an onset field as small as about 0.5 tesla. Despite the huge resistance, the oscillation profile, which exhibits many periods, mimics the Shubnikov–de Haas oscillations in metals. At ultralow temperatures, the observed oscillations evolve into discrete peaks near 1.6 tesla, above which the Landau quantized regime is fully developed. Such a low onset field of quantization is comparable to the behaviour of high-mobility conventional two-dimensional electron gases. Our experiments call for further investigation of the unusual ground state of the WTe2monolayer, including the influence of device components and the possible existence of mobile fermions and charge-neutral Fermi surfaces inside its insulating gap.