Magnetic Impurity in Insulators with Small Energy Gap
Magnetic Impurity in Insulators with Small Energy Gap
复制标题
小能隙绝缘体中的磁性杂质
DOI：
10.1143/jpsj.62.4364
复制
发表时间：
1993
影响因子：
1.7
通讯作者：
T. Saso
中科院分区：
文献类型：
--
作者：
J. Ogura;T. Saso
采用穷人标度、1/N展开、非交叉近似（NCA）内的自洽微扰方法以及量子蒙特卡罗（QMC）方法研究了小能隙绝缘体中磁性杂质的静态和动态性质。研究表明，当能隙增大时，磁性杂质的基态从单态变为多重态，这与BCS超导体中磁性杂质的情况类似，尽管与后者相比存在不同的特征。通过1/N展开和NCA发现能隙的临界值\(E_c\)为\(E_c/T_K = 2.0\)，而通过QMC得到\(E_c/T_K\approx0.4\sim0.9\)，其中\(T_K\)表示近藤温度。通过穷人标度发现，\(E_c\)会因能隙边缘的增强（变圆钝）而增大（减小）。
Static and dynamic properties of a magnetic impurity in insulators with a small energy gap are investigated by the poor man's scaling, 1/ N expansion, the self-consistent perturbation method within the non-crossing approximation (NCA) and the quantum Monte Carlo (QMC) method. It is shown that the ground state of the magnetic impurity changes from the singlet to multiplet when the gap increases, as in the case of the magnetic impurity in a BCS superconductor, although there is a different feature compared to the latter. Critical value of the gap E c is found to be E c / T K =2.0 by 1/ N expansion and NCA, while E c / T K ≈0.4∼0.9 by QMC, where T K denotes the Kondo temperature. It is found by the poor man's scaling that E c is enhanced (reduced) by the enhanced (rounded) gap-edge.