一维扩展量子罗盘模型的拓扑序和量子相变  

Topological orders and quantum phase transitions in a one-dimensional extended quantum compass model

作　　者：陈西浩[1,2] 王秀娟 Chen Xi-Hao;Wang Xiu-Juan(Postdoctoral Research Station of Material Science and Engineering,Chongqing University Chongqing 400030,China;State Key Laboratory of Power Transmission Equipment and System Security and New Technology,Chongqing University,Chongqing 400044,China;Department of Physics,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学材料科学与工程博士后流动站,重庆400030 [2]重庆大学物理学院,重庆400044 [3]重庆大学输配电装备及系统安全与新技术国家重点实验室,重庆400044

出　　处：《物理学报》2018年第19期50-56,共7页Acta Physica Sinica

摘　　要：应用矩阵乘积态表示的无限虚时间演化块算法,研究了扩展的量子罗盘模型.为了深入研究该模型的长程拓扑序和量子相变,基于奇数键和偶数键,引入了奇数弦关联和偶数弦关联,计算了保真度、奇数弦关联、偶数弦关联、奇数弦关联饱和性与序参量.弦关联表现出三种截然不同的行为:衰减为零、单调饱和与振荡饱和.基于弦关联的以上特征,给出了量子罗盘模型的基态序参量相图.在临界区,局域磁化强度和单调奇弦序参量的临界指数β=1/8表明:相变的普适类是Ising类型.此外,保真度探测到的相变点、连续性与非连续性和序参量的结果一致.By using the infinite time evolving block decimation in the presentation of infinite matrix product states, we study an extended quantum compass model（EQCM）. This model does not only include extremely rich phase diagrams due to competitions of orbital degrees of freedom and anisotropic couplings between pseudospin-1/2 operators but also have the capacity to describe property of protected qubits for quantum computation which leads to lots of attentions paid to the phase boundaries of the EQCM. However, few attentions are paid to long-range topological string correlation order parameters of the EQCM. To study order parameters, one should understand spontaneous symmetry breaking which relates to Landau quantum phase transitions theory. Once spontaneous symmetry breaking happens, there should exist some local order which can be described by a local order parameter. This order parameter can be used to distinguish the phase from others. For continuous quantum phase transitions, in the critical regime, critical exponents can be extracted.Unfortunately, the long-range topological string correlation orders are beyond Landau quantum phase transitions theory,one can not directly use two paradigms of Landau-Ginzburg-Wilson. Usually, one can define a local order parameter by local magnetization. Naturally, one can also refer to this way to define the long-range topological string correlation order parameters by long-range topological string correlations on the following conditions, i.e. the quantum system undergoes a hidden spontaneous symmetry breaking; the long-range topological string correlation order parameter can be used to distinguish the phase from others; for continuous quantum phase transitions, the long-range topological string correlation order parameter satisfies scaling law when control parameter getting close to critical point. Based on above idea, in order to characterize the topological ordered phases and quantum phase transitions in the EQCM, even/odd long-range topological string correlations are introd

关 键 词：量子相变 弦关联 拓扑序 临界指数 

分 类 号：O469[理学—凝聚态物理]