Bose-Fermi Anderson model with SU(2) symmetry: Continuous-time quantum Monte Carlo study
Bose-Fermi Anderson model with SU(2) symmetry: Continuous-time quantum Monte Carlo study
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DOI：
10.1103/physrevb.100.014439
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发表时间：
2019-07-30
影响因子：
3.7
通讯作者：
Si, Qimiao
中科院分区：
文献类型：
--
作者：
Cai, Ang;Si, Qimiao
在量子临界重费米子系统中，局域力矩与集体自旋涨落和传导电子相耦合。因此，描述局域时刻与玻色浴和费米浴的耦合的玻色-费米-安德森模型引起了广泛的兴趣。对于存在SU(2)自旋旋转对称性的模型，提出了关于其相图的问题。在这里，我们发展了一种适合于解决这个问题的连续时间量子蒙特卡罗(CT-QMC)方法；这个过程可以达到足够低的温度，同时保持SU(2)对称性。用这种方法对玻色-费米-安德森模型，我们阐明了重整化群不动点和相图的情况下，具有恒定费米浴密度和幂函数Rho(B)(欧米伽)成比例于欧米伽(S)(0<；S和lt；1)。重要的是，我们发现在一个模型中可以出现两种类型的近藤破坏量子临界点(QCP)。它们的区别在于近藤破坏态的性质：局域自旋关联要么在虚时间内按幂定律衰减，要么在长时间限制下保持不变。具体地说，对于S*<；S<；1的模型，这两种类型的QCP都存在，并且在解析的epsilon展开重整化群计算可获得的参数范围内(这里epsilon=1-S)，CT-QMC结果与用后一种方法先前的预测完全一致。对于S；S*来说，QCP只有一种类型。在这两种近藤破坏QCP中，我们发现局域自旋磁化率的指数。服从Eta=epsilon关系，这对Kondo晶格问题中的Kondo破坏QCP具有重要的意义。
In quantum critical heavy fermion systems, local moments are coupled to both collective spin fluctuations and conduction electrons. As such, the Bose-Fermi Anderson model, describing the coupling of a local moment to both a bosonic and a fermionic bath, has been of extensive interest. For the model in the presence of SU(2) spin rotational symmetry, questions have been raised about its phase diagram. Here we develop a version of continuous-time quantum Monte Carlo (CT-QMC) method suitable for addressing this issue; this procedure can reach sufficiently low temperatures while preserving the SU(2) symmetry. Using this method for the Bose-Fermi Anderson model, we clarify the renormalization-group fixed points and the phase diagram for the case with a constant fermionic-bath density of states and a power-law bosonic-bath spectral function rho(b)(omega) proportional to omega(s) (0 < s < 1). Importantly, we find that two types of Kondo destruction quantum critical point (QCP) can arise in a single model. They are distinguished by the nature of the Kondo destroyed state: The local spin correlation either decays in imaginary time as a power law or remains a constant in the long-time limit. Specifically, for the model with s* < s < 1, both types of QCPs exist and, in the parameter regime accessible by an analytical epsilon-expansion renormalization-group calculation (here epsilon = 1 - s), the CT-QMC result is fully consistent with prior predictions by the latter method. For s < s*, there is only one type of QCP. At both types of Kondo destruction QCPs, we find that the exponent of the local spin susceptibility. obeys the relation eta = epsilon, which has important implications for Kondo destruction QCP in the Kondo lattice problem.