Local fluctuations in quantum critical metals
Local fluctuations in quantum critical metals
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DOI：
10.1103/physrevb.68.115103
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发表时间：
2002-02
影响因子：
3.7
通讯作者：
Q. Si;S. Rabello;K. Ingersent;L. Smith
中科院分区：
文献类型：
--
作者：
Q. Si;S. Rabello;K. Ingersent;L. Smith
我们表明，空间局部，但低能量，波动可以发挥重要作用的物理强关联电子系统调谐到量子临界点。一个详细的微观分析的近藤晶格模型内进行了扩展的动态平均场方法。晶格模型的相关函数是通过自洽的玻色-费米近藤问题计算的，在该问题中，局部矩被耦合到费米子浴和玻色浴（波动磁场）。重整化群处理这个杂质问题-微扰在e= 1 - y，其中y是一个指数表征的玻色子浴光谱-表明，两个耦合之间的竞争可以驱动本地的时刻波动临界。结果，在近藤晶格中出现了两种不同类型的量子临界点，一种是通常的自旋密度波类型，另一种是“局部临界”。“在局部临界点附近，动力学自旋磁化率表现出分数指数的ω/T标度。当自旋密度波的临界点是高斯型时，局域临界点是长波长和空间局域临界模式共存的相互作用的固定点。讨论了局部临界点的Ginzburg-Landau描述。有人认为，这些结果是强大的，局部临界性提供了一个自然的描述的量子临界行为中看到的一些重费米子金属，这张照片也可能是相关的其他强相关的金属。
We show that spatially local, yet low-energy, fluctuations can play an essential role in the physics of strongly correlated electron systems tuned to a quantum critical point. A detailed microscopic analysis of the Kondo lattice model is carried out within an extended dynamical-mean-field approach. The correlation functions for the lattice model are calculated through a self-consistent Bose-Fermi Kondo problem, in which a local moment is coupled both to a fermionic bath and to a bosonic bath (a fluctuating magnetic field). A renormalization-group treatment of this impurity problem-perturbative in e= 1 - y, where y is an exponent characterizing the spectrum of the bosonic bath-shows that competition between the two couplings can drive the local-moment fluctuations critical. As a result, two distinct types of quantum critical point emerge in the Kondo lattice, one being of the usual spin-density-wave type, the other "locally critical." Near the locally critical point, the dynamical spin susceptibility exhibits ω/T scaling with a fractional exponent. While the spin-density-wave critical point is Gaussian, the locally critical point is an interacting fixed point at which long wavelength and spatially local critical modes coexist. A Ginzburg-Landau description for the locally critical point is discussed. It is argued that these results are robust, that local criticality provides a natural description of the quantum critical behavior seen in a number of heavy-fermion metals, and that this picture may also be relevant to other strongly correlated metals.