The Kondo effect of an adatom in graphene and its scanning tunneling spectroscopy
The Kondo effect of an adatom in graphene and its scanning tunneling spectroscopy
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石墨烯吸附原子的近藤效应及其扫描隧道光谱
DOI：
10.1088/1367-2630/15/5/053018
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发表时间：
2013-05-09
影响因子：
3.3
通讯作者：
Luo, Hong-Gang
中科院分区：
文献类型：
--
作者：
Li, Lin;Ni, Yang-Yang;Luo, Hong-Gang
我们研究了单个磁性吸附原子在石墨烯表面的近藤效应。石墨烯中狄拉克点附近独特的线性色散关系使磁性原子更容易形成局部磁矩，这简单地意味着可以在比金属宿主更宽的参数区域内观察到近藤共振。我们的研究表明，Kondo共振，当化学势被调谐远离狄拉克点，确实可以发生范围从Kondo政权，混合价，甚至空轨道政权定义在传统的金属主机。虽然近藤共振在近藤机制中表现为尖锐的峰，但它在混合价态和空轨道机制中具有峰谷结构和/或反共振，这是由于石墨烯中杂质水平的急剧加宽导致的显著背景而导致的Fano共振。我们还研究了吸附原子的扫描隧道显微镜（STM）光谱，它们显示出明显的粒子-空穴的不对称性时，化学势的调整施加到石墨烯的栅极电压。最后，我们探讨了STM针尖和石墨烯之间的直接隧穿通道对近藤共振的影响，发现近藤共振的线形不受影响，这可以归因于石墨烯中异常大的不对称因子。我们的研究表明，石墨烯是一个理想的平台，系统地研究近藤物理，这些结果是有用的，进一步刺激相关的实验研究系统。
We study the Kondo effect of a single magnetic adatom on the surface of graphene. The unique linear dispersion relation near the Dirac points in graphene makes it easier for the magnetic atom to form a local magnetic moment, which simply means that the Kondo resonance can be observed in a wider parameter region than in the metallic host. Our study indicates that the Kondo resonance, whenever the chemical potential is tuned away from the Dirac points, can indeed occur ranging from the Kondo regime, to the mixed valence, even to the empty orbital regime defined in the conventional metal host. While the Kondo resonance appears as a sharp peak in the Kondo regime, it has a peak-dip structure and/or an anti-resonance in the mixed valence and empty orbital regimes, which result from the Fano resonance due to the significant background due to dramatic broadening of the impurity level in graphene. We also study the scanning tunneling microscopy (STM) spectra of the adatom and they show obvious particle–hole asymmetry when the chemical potential is tuned by the gate voltages applied to the graphene. Finally, we explore the influence of the direct tunneling channel between the STM tip and the graphene on the Kondo resonance and find that the lineshape of the Kondo resonance is unaffected, which can be attributed to an unusually large asymmetry factor in graphene. Our study indicates that graphene is an ideal platform to systematically study Kondo physics and these results are useful to further stimulate relevant experimental studies on the system.