Magnetotransport Measurements of the Surface States of Samarium Hexaboride using Corbino Structures
Steven Wolgast, Yun Suk Eo, Teoman Ozturk, Gang Li, Ziji Xiang, Colin Tinsman, Tomoya Asaba, Ben Lawson, Fan Yu, J. W. Allen, Kai Sun, Lu Li, Cagliyan Kurdak, D… 展开作者
Steven Wolgast, Yun Suk Eo, Teoman Ozturk, Gang Li, Ziji Xiang, Colin Tinsman, Tomoya Asaba, Ben Lawson, Fan Yu, J. W. Allen, Kai Sun, Lu Li, Cagliyan Kurdak, Dae-Jeong Kim, Zachary Fisk
备注：
29 pages, 12 figures, PDFLaTeX. This new version is a combination of the prior version and arXiv:1410.7430
The recent conjecture of a topologically-protected surface state in SmB$_6$ and the verification of robust surface conduction below 4 K have prompted a large effort to understand the surface states. Conventional Hall transport measurements allow current to flow on all surfaces of a topological insulator, so such measurements are influenced by contributions from multiple surfaces of varying transport character. Instead, we study magnetotransport of SmB$_6$ using a Corbino geometry, which can directly measure the conductivity of a single, independent surface. Both (011) and (001) crystal surfaces show a strong negative magnetoresistance at all magnetic field angles measured. The (011) surface has a carrier mobility of $122\text{ cm}^2/\text{V}\cdot\text{sec}$ with a carrier density of $2.5\times10^{13} \text{ cm}^{-2}$, which are significantly smaller than indicated by Hall transport studies. This mobility value can explain a failure so far to observe Shubnikov-de Haas oscillations. Analysis of the angle-dependence of conductivity on the (011) surface suggests a combination of a field-dependent enhancement of the carrier density and a suppression of Kondo scattering from native oxide layer magnetic moments as the likely origin of the negative magnetoresistance. Our results also reveal a hysteretic behavior whose magnitude depends on the magnetic field sweep rate and temperature. Although this feature becomes smaller when the field sweep is slower, does not disappear or saturate during our slowest sweep-rate measurements, which is much slower than a typical magnetotransport trace. These observations cannot be explained by quantum interference corrections such as weak anti-localization, but are more likely due to an extrinsic magnetic effect such as the magnetocaloric effect or glassy ordering.
Hysteretic Magnetotransport in SmB6 at Low Magnetic Fields
利用Corbino圆盘结构，我们研究了低温下SmB 6在不同晶面上表面态的电阻率的磁场响应。我们的研究结果揭示了滞后行为，其大小取决于磁场扫描速率和温度。虽然这个功能变得更小时，场扫描速度较慢，一个完全消除或饱和，没有观察到在我们最慢的扫描速率测量，这是一个典型的磁输运轨迹慢得多。这些观测结果不能用量子干涉修正（如弱反定域）来解释。相反，它们是一致的玻璃表面磁有序的行为，其磁起源是最有可能从氧化钐（Sm 2 O 3）在暴露于环境条件下的表面上形成的。
