CAJ | 학술논문

采用第一性原理方法，对BaTi2 Bi2 O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。
채용제일성원리방법，대BaTi2 Bi2 O적전자결구화자성진행계산。비자성태적계산결과현시：비미능급처적태밀도주요래자dz2，dx2－y2화dxy삼개궤도，동시비미면야주요유삼부분조성，병차장기연착시량q1＝（π／a，0，0）화q2＝（0，π／a，0）평이시，제삼부분비미면（연착X?R련선）여제일부분비미면（M?A련선）감투명현，계산득출자화계수χ0（ q）재X점출현봉치，여봉치출현재M점적FeAs기초도체불동。상술자화솔봉치가이유도산생자선밀도파，사득BaTi2Bi2O재료적자성기태시bi?collinear antiferromagnetism（AF3）여blocked checkerboard antiferromagnetism （AF4）적이도간병태。수착공혈참잡，χ0（q）적봉치강저，이전자참잡칙도치봉치변대。당자선창락피완전압제시，초도출현，저가이해석위십요초도지출현재공혈참잡형화합물이비전자참잡형。
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.