栅极和局部曲率诱导石墨烯空位磁矩的康顿屏蔽。
Inducing Kondo screening of vacancy magnetic moments in graphene with gating and local curvature.
机构信息
Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ, 08855, USA.
Department of Physics, National Taiwan University, Taipei, 10617, Taiwan.
出版信息
Nat Commun. 2018 Jun 14;9(1):2349. doi: 10.1038/s41467-018-04812-6.
In normal metals the magnetic moment of impurity-spins disappears below a characteristic Kondo temperature which marks the formation of a cloud of conduction-band electrons that screen the local-moment. In contrast, moments embedded in insulators remain unscreened at all temperatures. What then is the fate of magnetic-moments in intermediate, pseudogap systems, such as graphene? Theory predicts that coupling to the conduction-band electrons will drive a quantum phase transition between a local-moment phase and a Kondo-screened phase. However, attempts to experimentally confirm this prediction and its intriguing consequences, such as electrostatically tunable magnetic-moments, have been elusive. Here we report the observation of Kondo-screening and the quantum phase-transition between screened and unscreened phases of vacancy magnetic moments in graphene. Using scanning tunneling spectroscopy and numerical renormalization-group calculations we show that this transition enables to control the screening of local moments by tuning the gate voltage and the local curvature of the graphene membrane.
在正常金属中，杂质自旋的磁矩在一个特征的康登温度以下消失，标志着导带电子云的形成，这些电子云屏蔽了局部磁矩。相比之下，嵌入在绝缘体中的磁矩在任何温度下都不会被屏蔽。那么，在中间的赝隙系统，如石墨烯中，磁矩的命运是什么呢？理论预测，与导带电子的耦合将驱动局部磁矩相和康登屏蔽相之间的量子相变。然而，实验上证实这一预测及其有趣的后果，如静电可调磁矩的尝试一直难以捉摸。在这里，我们报告了在石墨烯中观察到空位磁矩的康登屏蔽和屏蔽相与非屏蔽相之间的量子相变。通过扫描隧道光谱学和数值重整化群计算，我们表明，通过调节栅极电压和石墨烯膜的局部曲率，可以控制局部磁矩的屏蔽。
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