Dynamical Kondo effect and Kondo destruction in effective models for quantum-critical heavy fermion metals
Dynamical Kondo effect and Kondo destruction in effective models for quantum-critical heavy fermion metals
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发表时间：
2019-04
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通讯作者：
A. Cai;Haoyu Hu;K. Ingersent;S. Paschen;Q. Si
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作者：
A. Cai;Haoyu Hu;K. Ingersent;S. Paschen;Q. Si
某些重费米子金属的量子临界性被认为超出了序参量涨落的朗道框架。特别是，有相当多的证据表明近藤破坏：静态近藤单线态振幅的消失，导致费米面在量子临界点和额外的临界能量尺度上突然重建。这种效应可以用近藤和RKKY相互作用之间的动力学相互作用来分析。在近藤破坏阶段，一个定义明确的近藤共振丢失，但近藤单线态相关仍然在非零频率。这种动力学效应允许在近藤破坏阶段的质量增强。在这里，我们阐明了动力学Kondo效应玻色费米Kondo/安德森模型，明确地表现出Kondo破坏量子临界点。我们证明了一个简单的物理量--局部自旋（$f$）和传导电子自旋（$c$）的点积的期望值$\langle {\bf S}_{f} \cdot {\bf s}_{c} \rangle$--在这样的量子临界点上连续变化。一个非零的$\langle {\bf S}_{f} \cdot {\bf s}_{c} \rangle$表明了在近藤破坏相中运行的动力学近藤效应。讨论了近藤破坏量子临界的稳定性以及量子临界重费米子金属实验结果的理解的影响。
Quantum criticality in certain heavy-fermion metals is believed to go beyond the Landau framework of order-parameter fluctuations. In particular, there is considerable evidence for Kondo destruction: a disappearance of the static Kondo singlet amplitude that results in a sudden reconstruction of Fermi surface across the quantum critical point and an extra critical energy scale. This effect can be analyzed in terms of a dynamical interplay between the Kondo and RKKY interactions. In the Kondo-destroyed phase, a well-defined Kondo resonance is lost, but Kondo singlet correlations remain at nonzero frequencies. This dynamical effect allows for mass enhancement in the Kondo-destroyed phase. Here, we elucidate the dynamical Kondo effect in Bose-Fermi Kondo/Anderson models, which unambiguously exhibit Kondo-destruction quantum critical points. We show that a simple physical quantity---the expectation value $\langle {\bf S}_{f} \cdot {\bf s}_{c} \rangle$ for the dot product of the local ($f$) and conduction-electron ($c$) spins---varies continuously across such quantum critical points. A nonzero $\langle {\bf S}_{f} \cdot {\bf s}_{c} \rangle$ manifests the dynamical Kondo effect that operates in the Kondo-destroyed phase. Implications are discussed for the stability of Kondo-destruction quantum criticality as well as the understanding of experimental results in quantum critical heavy-fermion metals.