Unusual high-field metal in a Kondo insulator
Unusual high-field metal in a Kondo insulator
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DOI：
10.1038/s41567-021-01216-0
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发表时间：
2021-02
期刊：
影响因子：
19.6
通讯作者：
Z. Xiang;Lu Chen;Kuan-Wen Chen;C. Tinsman;Yuki Sato;T. Asaba;Helen Lu;Y. Kasahara;M. Jaime;F. Balakirev;F. Iga;Y. Matsuda;J. Singleton;Lu Li
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文献类型：
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作者：
Z. Xiang;Lu Chen;Kuan-Wen Chen;C. Tinsman;Yuki Sato;T. Asaba;Helen Lu;Y. Kasahara;M. Jaime;F. Balakirev;F. Iga;Y. Matsuda;J. Singleton;Lu Li
凝聚态系统中强的电子相互作用常常导致不寻常的量子相。一个这样的阶段发生在近藤绝缘体YbB 12，其绝缘状态表现出的现象是金属的特性，如磁量子振荡，一个无隙的费米子贡献的热容，和巡回费米子热输运。为了理解这些现象，研究它们在近藤绝缘体态的能隙被大磁场关闭时的演化是有益的。在这里，我们表明，明确的量子振荡观察所得的高场金属态的YbB 12，这是尽管它具有相对较高的电阻率，大的有效质量和巨大的Kadowaki-Woods比，一个组合，通常排除量子振荡。量子振荡频率和回旋质量都表现出强烈的场依赖性。通过跟踪费米表面积，我们得出结论，相同的准粒子带会在绝缘态和金属态引起量子振荡。这些数据最简单的理解是使用一个双流体的图片，其中中性准粒子-贡献很少或没有电荷传输-与带电费米子共存。我们的观察复杂的场依赖行为的费米子系综居住YbB 12提供了强有力的约束现有的理论模型。
Strong electronic interactions in condensed-matter systems often lead to unusual quantum phases. One such phase occurs in the Kondo insulator YbB12, the insulating state of which exhibits phenomena that are characteristic of metals, such as magnetic quantum oscillations, a gapless fermionic contribution to heat capacity,and itinerant-fermion thermal transport. To understand these phenomena, it is informative to study their evolution as the energy gap of the Kondo insulator state is closed by a large magnetic field. Here we show that clear quantum oscillations are observed in the resulting high-field metallic state in YbB12; this is despite it possessing relatively high resistivity, large effective masses and huge Kadowaki–Woods ratio, a combination that normally precludes quantum oscillations. Both quantum oscillation frequency and cyclotron mass display a strong field dependence. By tracking the Fermi surface area, we conclude that the same quasiparticle band gives rise to quantum oscillations in both insulating and metallic states. These data are understood most simply by using a two-fluid picture in which neutral quasiparticles—contributing little or nothing to charge transport—coexist with charged fermions. Our observations of the complex field-dependent behaviour of the fermion ensemble inhabiting YbB12provide strong constraints for existing theoretical models.