微扰法研究磁性原子在衬底上的近藤效应
A pertubative approach to the Kondo effect in magnetic atoms on nonmagnetic substrates
摘要：
扫描隧道显微镜的最新实验进展使测量衬底上孤立和磁耦合原子的电导谱成为可能。值得注意的是，这些光谱的特征在于近藤效应和自旋翻转非弹性电子隧穿之间的竞争。特别是，它们包括近藤共振和对数增强的电导在电压对应的磁激发，两个功能，不能被捕获的二阶微扰理论中的电子自旋耦合。我们导出了电子自旋自能的三阶解析表达式，它可以很容易地与有限偏压下电子输运的非平衡格林函数方案结合使用。我们证明，我们的方法是能够定量描述近藤共振和自旋翻转非弹性电子隧穿之间的竞争，计算成本显着低于其他方法。详细讨论了Co和Fe在CuN上的例子。
英文摘要：
Recent experimental advances in scanning tunneling microscopy make the measurement of the conductance spectra of isolated and magnetically coupled atoms on nonmagnetic substrates possible. Notably these spectra are characterized by a competition between the Kondo effect and spin-flip inelastic electron tunneling. In particular they include Kondo resonances and a logarithmic enhancement of the conductance at voltages corresponding to magnetic excitations, two features that cannot be captured by second order perturbation theory in the electron-spin coupling. We have now derived a third order analytic expression for the electron-spin self-energy, which can be readily used in combination with the non-equilibrium Green's function scheme for electron transport at finite bias. We demonstrate that our method is capable of quantitative description the competition between Kondo resonances and spin-flip inelastic electron tunneling at a computational cost significantly lower than that of other approaches. The examples of Co and Fe on CuN are discussed in detail.
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