Density-functional calculations of the electronic structures and magnetism of the pnictide superconductors ${\text{BaFeAs}}_2$ and ${\text{BaFeSb}}_2$

We investigate the structural, electronic, and magnetic properties of the hypothetical compound $\text{BaFe}P{n}_2$ ($Pn=\text{As}$ and Sb), which is isostructural to the parent compound of the high-temperature superconductor ${\text{LaFeAsO}}_{1-x}{\text{F}}_x$. Using density-functional theory, we show that the Fermi surface, electronic structure, and spin-density wave instability of $\text{BaFe}P{n}_2$ are very similar to the Fe-based superconductors. Additionally, there are very dispersive metallic bands of a spacer $Pn$ layer, which are almost decoupled from $\text{Fe}Pn$ layer. Our results show that experimental study of $\text{BaFe}P{n}_2$ can test the role of charge and polarization fluctuation as well as the importance of two dimensionality in the mechanism of superconductivity.

Figure 1

(Color) Crystal structure of $\text{BaFe}P{n}_2$ ($Pn=\text{As}$ and Sb). Ba, Fe, $Pn\left(1\right)$, and $Pn\left(2\right)$ atoms are denoted by gray, red, orange, and yellow spheres, respectively. There are two type of $Pn$: $Pn\left(1\right)$ in $\text{B}Pn$ layer and $Pn\left(2\right)$ in $\text{Fe}Pn$ layer. Isostructural compound LaFeAsO has the similar structure of LaO layer with $\text{Ba}Pn\left(1\right)$ layer.

Figure 2

(Color) Total and partial DOS of ${\text{BaFeAs}}_2$ and ${\text{BaFeSb}}_2$.

Figure 3

(Color online) Band structure of ${\text{BaFeAs}}_2$ and ${\text{BaFeSb}}_2$.

Figure 4

(Color) Fermi surfaces of ${\text{BeFeAs}}_2$ and ${\text{BaFeSb}}_2$ in the first Brillouin zone centered at the $\Gamma$ point.