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arXiv 0707.4152cond-mat.mes-hallcond-mat.str-el
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金属中SU(3)量子缺陷的稳定双通道Kondo不动点:重整化群分析和电导尖峰

Stable two-channel Kondo fixed point of an SU(3) quantum defect in a metal: renormalization group analysis and conductance spikes

Michael Arnold, Tobias Langenbruch, Johann Kroha

摘要:

我们提出了一种双通道近藤(2CK)效应的物理实现,其中金属中的动力学缺陷具有唯一的基态和双重简并激发态。在很宽的参数范围内,与电子的相互作用使激发的双态重正化,使其低于裸缺陷基态,从而稳定2CK固定点。除了近藤温度T_K外,三态缺陷还表现出另一个低能标度,它与基态到激发态的跃迁有关,可以指数地小于T_K。使用微扰非平衡重整化群,我们明确表明,这可以提供长期寻求的解释,观察到的尖锐的电导尖峰拉尔夫和Buhrman在超小金属点接触。

英文摘要:

We propose a physical realization of the two-channel Kondo (2CK) effect, where a dynamical defect in a metal has a unique ground state and twofold degenerate excited states. In a wide range of parameters the interactions with the electrons renormalize the excited double downward below the bare defect ground state, thus stabilizing the 2CK fixed point. In addition to the Kondo temperature T_K the three-state defect exhibits another low-energy scale, associated with ground-to-excited-state transitions, which can be exponentially smaller than T_K. Using the perturbative nonequilibrium renormalization group we demonstrate explicitly that this can provide the long-sought explanation of the sharp conductance spikes observed by Ralph and Buhrman in ultrasmall metallic point contacts.

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