Through the Jordan-Wigner transformation,the entanglement entropy and ground state phase diagrams of exactly solvable spin model with alternating and multiple spin exchange interactions are investigated by means of Gr...Through the Jordan-Wigner transformation,the entanglement entropy and ground state phase diagrams of exactly solvable spin model with alternating and multiple spin exchange interactions are investigated by means of Green's function theory.In the absence of four-spin interactions,the ground state presents plentiful quantum phases due to the multiple spin interactions and magnetic fields.It is shown that the two-site entanglement entropy is a good indicator of quantum phase transition (QPT).In addition,the alternating interactions can destroy the magnetization plateau and wash out the spin-gap of low-lying excitations.However,in the presence of four-spin interactions,apart from the second order QPTs,the system manifests the first order QPT at the tricritical point and an additional new phase called "spin waves",which is due to the collapse of the continuous tower-like low-lying excitations modulated by the four-spin interactions for large three-spin couplings.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.10774051 and 10804034the National 973 Project under Grant No.2006CB921605+1 种基金the Research Fund for the Doctoral Program of Higher Education under Grant No.20090142110063the National Science Foundation of Hubei Province of China under Grant No.2008CDB003
文摘Through the Jordan-Wigner transformation,the entanglement entropy and ground state phase diagrams of exactly solvable spin model with alternating and multiple spin exchange interactions are investigated by means of Green's function theory.In the absence of four-spin interactions,the ground state presents plentiful quantum phases due to the multiple spin interactions and magnetic fields.It is shown that the two-site entanglement entropy is a good indicator of quantum phase transition (QPT).In addition,the alternating interactions can destroy the magnetization plateau and wash out the spin-gap of low-lying excitations.However,in the presence of four-spin interactions,apart from the second order QPTs,the system manifests the first order QPT at the tricritical point and an additional new phase called "spin waves",which is due to the collapse of the continuous tower-like low-lying excitations modulated by the four-spin interactions for large three-spin couplings.
