BaTi_2Bi_2O的电子结构与磁性  

Electronic Structure and Magnetism of BaTi_2Bi_2O

作　　者：王广涛[1] 张琳[1] 张会平[1] 刘畅[1] 

机构地区：[1]河南师范大学物理与电子工程学院,河南新乡453007

出　　处：《计算物理》2015年第1期107-114,共8页Chinese Journal of Computational Physics

基　　金：国家自然基金(11274095);河南省高校创新人才(2012HASTIT009)资助项目

摘　　要：采用第一性原理方法,对BaTi2Bi2O的电子结构和磁性进行计算.非磁性态的计算结果显示:费米能级处的态密度主要来自dz2,dx2-y2和dxy三个轨道,同时费米面也主要有三部分组成,并且将其沿着矢量q1=(π/a,0,0)和q2=(0,π/a,0)平移时,第三部分费米面(沿着X-R连线)与第一部分费米面(M-A连线)嵌套明显,计算得出磁化系数χ0(q)在X点出现峰值,与峰值出现在M点的FeAs基超导体不同.上述磁化率峰值可以诱导产生自旋密度波,使得BaTi2Bi2O材料的磁性基态是bi-collinear antiferromagnetism(AF3)与blocked checkerboard antiferromagnetism(AF4)的二度简并态.随着空穴掺杂,χ0(q)的峰值降低,而电子掺杂则导致峰值变大.当自旋涨落被完全压制时,超导出现,这可以解释为什么超导只出现在空穴掺杂型化合物而非电子掺杂型.Electronic structure and magnetic structures of BaTi2 Bi2 O are studied with first-principles calculations. In nonmagnetic state, density of states at Fermi level are mostly derived from dz2 , dx2-y2 and dxy orbitals. Fermi surface （ FS） consists of three sheets. The third FS sheet （along X-R line） nests with the first FS sheet （along M-A line） by q-vector q1 =（π/a,0,0） or q2 =（0,π/a,0） shift. Calculated bare susceptibility χ0 （ q） peaked at X-point, rather than at M-point in FeAs-based superconductors. Such peaked susceptibility induces spin density wave （SDW）. Magnetic ground state is nearly two degenerate antiferromagnetism of bi-collinear antiferromagnetism （AF3） and blocked checkerboard antiferromagnetism （AF4）. Peak of susceptibilityχ0（q） is obviously suppressed and becomes slightly in-commensurate with hole doping, but increased with electron doping. As spin fluctuation is suppressed superconductivity appears. It explains that superconductivity appears only in hole-doped compounds, and not in electron-doped ones.

关 键 词：第一性原理 费米面嵌套 超导 

分 类 号：O469[理学—凝聚态物理]