In correlated electronic systems, strong interactions and the interplay between different degrees of freedom may give rise to anomalous charge-transport properties, which can be tuned by external parameters like temperature and magnetic field. Recently, magnetic quantum oscillations and metallic low-temperature thermal conductivity have been observed in the Kondo insulator ${\mathrm{YbB}}_{12}$, whose resistivity is a few orders of magnitude higher than those of conventional metals. As yet, these unusual observations are not fully understood. Here we present a detailed investigation of the behavior of ${\mathrm{YbB}}_{12}$ under intense magnetic fields using both transport and torque magnetometry measurements. The Hall resistivity displays a strongly nonlinear field dependence which cannot be described using a standard two-band Drude model. A low-field Hall anomaly, reminiscent of the Hall response associated with “strange-metal” physics, develops at $T<1.5\mathrm{K}$. At two characteristic magnetic fields (${\mu }_0{H}_1=19.6\mathrm{T}$ and ${\mu }_0{H}_2\sim 31\mathrm{T}$), signatures appear in the Hall coefficient, magnetic torque, and magnetoresistance; the latter characteristic field coincides with the occurrence of a change in quantum-oscillation frequency. We suggest that they are likely to be field-induced Lifshitz transitions. Moreover, above 35 T, where the most pronounced quantum oscillations are detected, the background resistivity displays an unusual, nonmetallic $T^{\alpha }$ behavior, with $\alpha$ being field dependent and varying between $-1.5$ and $-2$ By normalizing the Shubnikov–de Haas oscillation amplitude to this $T^{\alpha }$ dependence, the calculated cyclotron mass becomes more consistent with that deduced from de Haas–van Alphen oscillations. Our results support a novel two-fluid scenario in ${\mathrm{YbB}}_{12}$: A Fermi-liquid-like fluid of charge-neutral quasiparticles coexists with charge carriers that remain in a nonmetallic state. The former experience successive Lifshitz transitions and develop Landau quantization in applied magnetic fields, while scattering between both fluids allows the Shubnikov–de Haas effect to be observed in the electrical transport. The verification of this two-fluid scenario by the data in the current work strongly suggests that ${\mathrm{YbB}}_{12}$ represents a new phase of matter.

中文翻译：

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Kondo 绝缘体 YbB12 中的霍尔异常、量子振荡和可能的 Lifshitz 跃迁：非常规电荷传输的证据

在相关电子系统中，强相互作用和不同自由度之间的相互作用可能会导致异常的电荷传输特性，这些特性可以通过温度和磁场等外部参数进行调整。最近，在近藤绝缘体中观察到磁量子振荡和金属低温热导率${\mathrm{YbB}}_{12}$，其电阻率比传统金属高几个数量级。到目前为止，这些不寻常的观察还没有被完全理解。在这里，我们将详细调查他们的行为${\mathrm{YbB}}_{12}$在强磁场下使用传输和扭矩磁力测量。霍尔电阻率显示出强烈的非线性场依赖性，这无法使用标准的双波段 Drude 模型来描述。一个低场霍尔异常，让人想起与“奇异金属”物理相关的霍尔响应，在$吨<1.5\mathrm{ķ}$. 在两个特征磁场（${\mu }_0{H}_1=19.6\mathrm{吨}$和${\mu }_0{H}_2～31\mathrm{吨}$)，签名出现在霍尔系数、磁转矩和磁阻中；后一个特征场与量子振荡频率的变化相吻合。我们认为它们很可能是场诱导的 Lifshitz 跃迁。此外，在 35 T 以上，检测到最明显的量子振荡，背景电阻率显示出不寻常的非金属${吨}^{\alpha }$行为，与$\alpha$依赖于场并且在$-1.5$和$-2$通过将 Shubnikov-de Haas 振荡幅度归一化为${吨}^{\alpha }$依赖关系，计算出的回旋加速器质量变得更符合从德哈斯-范阿尔芬振荡推导的质量。我们的结果支持一种新的两流体场景${\mathrm{YbB}}_{12}$：电荷中性准粒子的类费米液体流体与保持非金属状态的电荷载体共存。前者经历了连续的 Lifshitz 跃迁并在应用磁场中发展了朗道量子化，而两种流体之间的散射允许在电传输中观察到 Shubnikov-de Haas 效应。当前工作中的数据对这种两流体情景的验证强烈表明，${\mathrm{YbB}}_{12}$代表物质的一个新阶段。