The electronic structure and magnetism of BaTi2Sb2O

Abstract

The electronic structure and magnetic structures of recently discovered BaTi2Sb2O were studied from first-principles calculations. In the nonmagnetic state, the density of states at the Fermi level are mostly derived from the dz2,dx2−y2, and dxy orbitals. The Fermi surface (FS) consists of three sheets. The first FS sheet (along X-R line) will nest with the third FS sheet (along M-A line) by the q-vector q→1=(πa, 0, 0) or q→2=(0,πa, 0) shift. The calculated bare susceptibility χ0(q) peaked at X-point, rather than at the M-point in the FeAs-based superconductor. Such peaked susceptibility induces the spin density wave, 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 χ0(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.