界面铁掺杂锯齿形石墨烯纳米带的自旋输运性能  

Spin transport properties for iron-doped zigzag-graphene nanoribbons interface

作　　者：邓小清[1] 孙琳[1] 李春先[1] 

机构地区：[1]长沙理工大学物理与电子科学学院,长沙410114

出　　处：《物理学报》2016年第6期345-351,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61371065;61201080);湖南省自然科学基金(批准号:2015JJ3002);湖南省重点学科建设项目;湖南省高校科技创新团队支持计划;长沙理工大学创新项目资助的课题~~

摘　　要：基于密度泛函理论第一原理系统研究了界面铁掺杂锯齿(zigzag)形石墨烯纳米带的自旋输运性能,首先考虑了宽度为4的锯齿(zigzag)形石墨烯纳米带,构建了4个纳米器件模型,对应于中心散射区的长度分别为N=4,6,8和10个石墨烯单胞的长度,铁掺杂在中心区和电极的界面.发现在铁磁(FM)态,四个器件的β自旋的电流远大于α自旋的电流,产生了自旋过滤现象;而界面铁掺杂的反铁磁态模型,两种电流自旋都很小,无法产生自旋过滤现象;进一步考虑电极的反自旋构型,器件电流显示出明显的自旋过滤效应.探讨了带宽分别为5和6的纳米器件的自旋输运性能,中心散射区的长度为N=6个石墨烯单胞的长度,FM态下器件两种自旋方向的电流值也存在较大的差异,β自旋的电流远大于α自旋电流.这些结果表明:界面铁掺杂能有效调控锯齿形石墨烯纳米带的自旋电子,对于设计和发展高极化自旋过滤器件有重要意义.By using the first-principles method based on the density-functional theory, the spin transport properties for the systems consisting of iron-doped zigzag-edged graphene nanoribbons（ZGNRs） with iron doping at the interface, where the connection is realized between electrodes and the central scattering region, are investigated theoretically. The ribbon widths of ZGNRs are four zigzag C chains（4 ZGNRs）, and the length of scattering region is N unit cells（here, N = 4,6, 8, 10）. Results show that β-spin current is obviously greater than the α-spin current under the ferromagnetic（FM）configuration, which is the spin filtering effect. The reason of spin filtering effect cames from two aspects： a） The symmetry-dependent transport properties which arise from different coupling rules between the π and π＊subbands around the Fermi level, that are dependent on the wave-function symmetry of the two subbands; b） the distribution of molecular orbit within the bias windows, location, or delocalization. While for antiferromagnetic（AFM） spin state,both α and β spin currents are very small and both the positive and negative bias regions originate from the existence of band gap; therefore, no obvious spin filtering effect can be obtained. For antiparallel（AP） magnetism configuration,spin filtering effect also can be obtained at high bias. Next, we also investigate the other models： the ribbon width of ZGNRs is five（six） zigzag C chains, namely, 5 ZGNRs（6 ZGNRs）, and the scattering region is 6 unit cells length.The currents in 6 ZGNRs are less than that of 5 ZGNRs obviously, and this difference is revealed to arise from different couplings between the conducting subbands around the Fermi level, which is dependent on the symmetry of the systems.However, both of the two models show the similar characteristic： spin filtering effect. The β spin current is obviously greater than the α-spin current with the whole bias under the ferromagnetic（FM） configuration, The analysis on the elect

关 键 词：石墨烯纳米带 自旋输运 自旋过滤效应 第一性原理方法 

分 类 号：O469[理学—凝聚态物理]