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arXiv 0808.2647cond-mat.str-el
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Berry相与Bose-Fermi Kondo模型量子临界点的量子到经典映射的破缺

Berry Phase and the Breakdown of the Quantum to Classical Mapping for the Quantum Critical Point of the Bose-Fermi Kondo model

Stefan Kirchner, Qimiao Si

摘要:

玻色-费米近藤模型的相图包含一个SU(2)不变的近藤屏蔽相,它与近藤破坏的局域矩相被一个连续的量子相变分开。我们分析了自旋路径积分中的Berry相位项对该量子杂质模型的量子临界性质的影响。对于表征耗散玻色浴谱密度的幂律指数的范围,忽略Berry相位项的影响使得不动点为高斯型。对于相同的谱密度指数范围,引入Berry相位项会导致一个相互作用的不动点,在这个不动点上,量子到经典的映射失效。我们的研究结果的一些一般意义进行了讨论。

英文摘要:

The phase diagram of the Bose-Fermi Kondo model contains an SU(2)-invariant Kondo-screened phase separated by a continuous quantum phase transition from a Kondo-destroyed local moment phase. We analyze the effect of the Berry phase term of the spin path integral on the quantum critical properties of this quantum impurity model. For a range of the power-law exponent characterizing the spectral density of the dissipative bosonic bath, neglecting the influence of the Berry phase term makes the fixed point Gaussian. For the same range of the spectral density exponent, incorporating the Berry phase term leads instead to an interacting fixed point, for which a quantum to classical mapping breaks down. Some general implications of our results are discussed.

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