Department of Physics, University of Basel, Basel, Switzerland.
Nanotechnology. 2011 Jul 1;22(26):265204. doi: 10.1088/0957-4484/22/26/265204. Epub 2011 May 17.
We show a detailed investigation of the split Kondo effect in a carbon nanotube quantum dot with multiple gate electrodes. Two conductance peaks, observed at finite bias in nonlinear transport measurements, are found to approach each other for increasing magnetic field, to result in a recovered zero bias Kondo resonance at finite magnetic field. Surprisingly, in the same charge state, but under different gate configurations, the splitting does not disappear for any value of the magnetic field, but we observe an avoided crossing. We think that our observations can be understood in terms of a two-impurity Kondo effect with two spins coupled antiferromagnetically. The exchange coupling between the two spins can be influenced by a local gate, and the non-recovery of the Kondo resonance for certain gate configurations is explained by the existence of a small antisymmetric contribution to the exchange interaction between the two spins.
我们对具有多个栅极电极的碳纳米管量子点中的分裂 Kondo 效应进行了详细研究。在非线性输运测量中，在有限偏压下观察到两个电导峰，发现它们随着磁场的增加而相互接近，导致在有限磁场下恢复零偏压 Kondo 共振。令人惊讶的是，在相同的电荷状态下，但在不同的栅极配置下，分裂不会在任何磁场值下消失，而是我们观察到一个避免交叉。我们认为，我们的观察结果可以用两个自旋反铁磁耦合的双杂质 Kondo 效应来理解。两个自旋之间的交换耦合可以受到局部栅极的影响，对于某些栅极配置，Kondo 共振的未恢复可以通过两个自旋之间的交换相互作用存在小的反对称贡献来解释。
