论文标题
Kondo绝缘子SMB $ _ {6} $中的金属群岛
Metallic islands in the Kondo insulator SmB$_{6}$
论文作者
论文摘要
SMB $ _ {6} $中近代物理学与非平凡拓扑之间的预测相互作用激发了许多实验报告，其中一些显然是矛盾的。争端的起源可能在于在SM空缺（近孔孔）和/或自然杂质（例如GD $^{3+} $）的情况下，近托绝缘阶段的脆弱性。在这项工作中，我们在本地研究了Al-Flux种植的SM $ _ {1-x} $ gd $ _ {x} $ b $ _ {6} $单晶（0 $ \ leq $ $ x $ x $ \ $ \ leq $ 0.02）的这种脆弱性，通过将电子旋转共振（ESR）和富含互补的测量结合在一起。 GD $^{3+} $ ESR Spectra以高度稀释的制度（$ x $ $ \ sim 0.0004 $）显示了绝缘立方环境的功能。值得注意的是，即使这些系统仍处于相当稀释的状态并显示出绝缘$ DC $电阻率，但观察到金属ESR线形（$ x $ $ \ geq $ 0.004）也观察到金属ESR线形。我们的数据表明，在全球渗透发生之前，围绕杂质围绕当地破坏了近托绝缘状态。该结果不仅解释了$ dc $和$ ac $电导率之间的差异，而且还提供了一种场景，以解释在不存在电阻率中量子振荡的情况下磁化中量子振荡的存在。
The predicted interplay between Kondo physics and non-trivial topology in SmB$_{6}$ has stimulated many experimental reports, some of which are in apparent contradiction. The origin of the dispute may lie on the fragility of the Kondo insulating phase in the presence of Sm vacancies (Kondo holes) and/or natural impurities, such as Gd$^{3+}$. In this work, we locally investigated this fragility for Al-flux grown Sm$_{1-x}$Gd$_{x}$B$_{6}$ single crystals (0 $\leq$ $x$ $\leq$ 0.02) by combining electron spin resonance (ESR) and complementary bulk measurements. The Gd$^{3+}$ ESR spectra in a highly dilute regime ($x$ $\sim 0.0004$) display the features of an insulating cubic environment. Remarkably, a metallic ESR lineshape is observed for more concentrated samples ($x$ $\geq$ 0.004), even though these systems are still in a reasonably dilute regime and show insulating $dc$ electrical resistivity. Our data indicate that the Kondo insulating state is destroyed locally around impurities before a global percolation occurs. This result not only explains the discrepancy between $dc$ and $ac$ conductivity, but also provides a scenario to explain the presence of quantum oscillations in magnetization in the absence of quantum oscillations in electrical resistivity.
