Phase Diagram of the BCS–Hubbard Model in a Magnetic Field

作     者：Dong-Hong Xu Yi-Cong Yu Xing-Jie Han Xi Chen Kang Wang Ming-Pu Qin Hai-Jun Liao Tao Xiang Dong-Hong Xu;Yi-Cong Yu;Xing-Jie Han;Xi Chen;Kang Wang;Ming-Pu Qin;Hai-Jun Liao;Tao Xiang

作者机构：Beijing National Laboratory for Condensed Matter Physics and Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical SciencesUniversity of Chinese Academy of SciencesBeijing 100049China Wuhan Institute of Physics and MathematicsIAPMSTChinese Academy of SciencesWuhan 430071China School of ScienceBeijing University of Posts and TelecommunicationsBeijing 100876China Key Laboratory of Artificial Structures and Quantum ControlSchool of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Songshan Lake Materials LaboratoryDongguan 523808China Beijing Academy of Quantum Information SciencesBeijing 100193China 

出 版 物：《Chinese Physics Letters》 (中国物理快报（英文版）)

年 卷 期：2022年第39卷第6期

页      面：24-28页

核心收录：

学科分类：07[理学] 070205[理学-凝聚态物理] 0702[理学-物理学] 

基　　金：supported by the National Key Research and Development Program of China (Grant No. 2017YFA0302901) the National Natural Science Foundation of China (Grants Nos. 11888101 and 11874095) the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB33000000) the Youth Innovation Promotion Association CAS (Grants No. 2021004) 

主　　题：temperature field Hubbard 

摘      要：We propose an extended BCS–Hubbard model and investigate its ground state phase diagram in an external magnetic field.By mapping the model onto a model of spinless fermions coupled with conserving Z_(2) variables which are mimicked by pseudospins,the model is shown to be exactly solvable along the symmetric lines for an arbitrary on-site Hubbard interaction on the bipartite lattice.In the zero field limit,the ground states exhibit an antiferromagnetic order of pseudospins.In the large field limit,on the other hand,the pseudospins are fully polarized ordered.With the increase of the applied field,a first-order phase transition occurs between these kinds of phases when the on-site Coulomb interaction is less than a critical value U(c).Above this critical U_(c),a novel intermediate phase emerges between the fully polarized and antiferromagnetic phases.The ground states in this phase are macroscopically degenerate,like in a spin ice,and the corresponding entropy scales linearly with the lattice size at zero temperature.