BaTi_2Bi_2O的电子结构与磁性（英文）  

THE ELECTRONIC STRUCTURE AND MAGNETISM OF BaTi_2Bi_2O

作　　者：王广涛[1] 张会平[1] 张林[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：《低温物理学报》2014年第4期249-256,共8页Low Temperature Physical Letters

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.11274095)~~

摘　　要：采用第一性原理计算,我们对BaTi2Bi2O材料的电子结构和磁性做了详细的研究.其非磁性态的计算结果显示,费米能级处的态密度主要来自d2 z,d x2-y2和dxy三个轨道的电子.费米面主要有三部分组成,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)a嵌套明显,计算得出磁化系数χ0(q)值出现在在X点出现峰值,这一点与峰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,这使得BaTi2Bi2O的磁性基态是能量基本简并的bi-collinear antiferromagnetism(AF3)与blocked checkerboard antiferromagnetism(AF4)磁性态.随着空穴掺杂,χ0(q)的峰值降低并且变得有些不对称,而电子掺杂则导致峰值变大.一般认为超导序和磁性序相互竞争,当自旋涨落被完全压制时,超导出现,这正好可以解释为什么超导只能出现在空穴掺杂型化合物而非电子掺杂型里.The electronic structure and magnetic structures of recently discovered BaTi2 Bi20 was studied from first-principles calculations. In the nonmagnetic state, the density of states at the Fermi level are mostly derived fromthe dz2 , dx2_y2 and dxy orbitals. The Fermi surface （FS） consists of three sheets. The third FS sheet （along X- R line） will nest with the first FS sheet （along M-A line） by the q-vector q1 = （π/a,0,0） or q2 = （0, π/a ,0） shift. The calculated bare susceptibility x0 （q） peaked at X-point, rather than at the M-point in the FeAs-based superconductor. Such peaked susceptibility induces the spin density wave （SDW）, and the magnetic ground state is nearly two degenerate antiferromagnetism, the bi-collinear antiferromagnetism （AF3） or the blocked checkerboard antiferromagnetism （AF4）. The peak of susceptibility x0 （q） is obviously suppressed and become slightly in- commensurate with hole doping, but increased with electron doping. When the spin fluctuation is suppressed, the superconductivity appears. This can explain that why the superconductivity appears only in the hole-doped compounds, not in the electron-doped ones.

关 键 词：第一原理计算 费米面嵌套 超导 

分 类 号：O482.5[理学—固体物理]