摘要
By using the coupled duster method and the numerical density matrix renormalization group method, we investigate the properties of the quantum plateau state in an alternating Heisenberg spin chain. In the absence of a magnetic field, the results obtained from the coupled cluster method and density matrix renormalization group method both show that the ground state of the aiternating chain is a gapped dimerized state when the parameter a exceeds a critical point ac. The value of the critical points can be determined precisely by a detailed investigation of the behavior of the spin gap. The system therefore possesses an m = 0 plateau state in the presence of a magnetic field When a 〉 ac. In addition to the m = 0 plateau state, the results of density matrix renormaiization group indicate that there is an m = 1/4 plateau state that occurs between two critical fields in the alternating chain if a 〉 1. The mechanism for the m = 1/4 plateau state and the critical behavior of the magnetization as one approaches this plateau state are also discussed.
基金
Supported by the National Natural Science Foundation of China under Grant Nos.10804053 and 61203147
the Natural Science Foundation of Jiangsu Province under Grant No.BK20131428
the Natural Science Foundation of the Jiangsu Higher Education Institutions under Grant No.13KJD140003
the Scientific Research Foundation of Nanjing University of Posts and Telecommunications under Grant No.NY211008
Qing Lan Project of Jiangsu Province