期刊
NANO LETTERS
卷 14, 期 7, 页码 4011-4015出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl501425n
关键词
Kondo effect; scanning tunneling microscopy; graphene; magnetic impurity; surface adsorption
类别
资金
- National Natural Science Foundation of China [51210003, 61390500, 61274011, 11325417]
- National 973 projects of China [2011CB309703, 2013CBA01600]
- Chinese Academy of Sciences
- Shanghai supercomputer center
- U.S. DOE Office of Basic Energy Sciences
- Vanderbilt by the McMinn Endowment
- U.S. DOE
The Kondo effect, a widely studied phenomenon in which the scattering of conduction electrons by magnetic impurities increases as the temperature T is lowered, depends strongly on the density of states at the Fermi energy. It has been predicted by theory that magnetic impurities on free-standing monolayer graphene exhibit the Kondo effect and that control of the density of states at the Fermi level by external means can be used to switch the effect on and off. However, though transport data for Co adatoms on graphene monolayers on several substrates have been reported, there exists no evidence for a Kondo effect. Here we probe the role of the substrate on the Kondo effect of Co on graphene by combining low-temperature scanning tunneling microscopy and spectroscopy measurements with density functional theory calculations. We use a Ru(0001) substrate that is known to cause graphene to ripple, yielding a moire superlattice. The experimental data show a sharp Kondo resonance peak near the Fermi energy from only Co adatoms at the edge of atop regions of the moire pattern. The theoretical results show that the variation of the distance from the graphene to the Ru substrate, which controls the spin polarization and local density of states at the Fermi energy, is the key factor for the appearance of the Kondo resonance. The results suggest that rippling of graphene by suitable substrates is an additional lever for tuning and selectively switching the appearance of the Kondo effect.
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