塞曼场下狄拉克费米子系统的输运与磁序转变  

Transport and magnetic transition of Dirac fermion systems in Zeeman field

作　　者：孟敬尧 郭恺怡 梁颖[1] MENG Jingyao;GUO Kaiyi;LIANG Ying(Department of Physics,Beijing Normal University,100875,Beijing,China;Beijing Computational Science Research Center,100193,Beijing,China)

机构地区：[1]北京师范大学物理学系,北京100875 [2]北京计算科学研究中心,北京100193

出　　处：《北京师范大学学报（自然科学版）》2023年第6期926-933,共8页Journal of Beijing Normal University(Natural Science)

基　　金：国家自然科学基金资助项目(11974049)。

摘　　要：利用行列式量子蒙特卡罗方法,研究了二维石墨烯晶格中塞曼场诱导的相变.库仑斥力U、无序Δ和磁场B之间的竞争将原本是半金属的状态驱动到具有不同特征的绝缘相,且对于塞曼场诱发的带绝缘相,增强电子相互作用和键无序,将有效降低相变需要的临界磁场.随着磁场持续增加,磁场诱发对称性破缺进而诱发反铁磁相,最终系统进入完全自旋极化状态.在电子关联系统中,弱相互作用会促进磁场对反铁磁的效应;然而当U>Uc=4.5时,相互作用继续增加将抑制该效应的强度.平行磁场的引入,为在实际材料中观察到输运转变和磁转变提供了可能.Since Slater suggested that a gap could be opened by magnetic ordering with spin-dependent electronic energy,applying magnetic field has been a powerful means to tune properties of Dirac fermion systems,especially of the 2D graphene system.Determinant quantum Monte Carlo(DQMC)method is used,to investigate phase transitions induced by Zeeman field in 2D graphene lattice.Competition between Coulomb repulsion U,disorderΔand magnetic fields B drives semimetallic regime to insulating phases exhibiting different characters.Further,critical Zeeman field Bc triggering band-insulator is largely reduced by the presence of interaction and disorder.As magnetic field continues to increase,B-induced symmetry breaking introduces an antiferromagnetic(AFM)phase,and eventually the system enters a fully spin-polarized state.In correlated system,weak interaction would enhance the effect of magnetic field on AFM phase,while strong interaction larger than Uc=4.5 would inhibit this effect.Applying parallel magnetic fields provides the possibility to observe transport and magnetic transitions in real materials.

关 键 词：石墨烯 塞曼场 HUBBARD模型 行列式量子蒙特卡罗(DQMC)方法 

分 类 号：O469[理学—凝聚态物理]