Semimetallic spin-density wave state in iron pnictides

We examine the existence of semimetallic spin-density wave (SDW) states in iron pnictides. In the experimentally observed metallic SDW state, the symmetry-protected Dirac cones are located away from the Fermi surface giving rise to tiny pockets and there are also additional Fermi pockets such as one around Gamma. We find that the location of a pair of Dirac points with respect to the Fermi surface exhibits significant sensitivity to the orbital splitting between the d ( xz ) and d ( yz ) orbitals. Besides, in the presence of orbital splitting, the Fermi pockets not associated with the Dirac cones, can be suppressed so that a semimetallic SDW state can be realized. We explain these findings in terms of difference in the slopes and orbital contents of the bands which form the Dirac cone, and obtain the necessary conditions dependent on these two and other parameters for the coexisting Dirac semimetallic and SDW states. Additionally, the topologically protected edge states are studied in the ribbon geometry when the same are oriented either along x or y axes.

Automated summary

We investigate the existence of semimetallic spin-density wave (SDW) states in iron pnictides. It is found that the position of a pair of Dirac points with respect to the Fermi surface shows sensitivity to the orbital splitting between the d(xz) and d(yz) orbitals. In the presence of orbital splitting, the Fermi pockets not associated with the Dirac cones can be suppressed, leading to the realization of a semimetallic SDW state. The necessary conditions for coexisting Dirac semimetallic and SDW states are obtained based on the difference in slopes and orbital contents of the bands forming the Dirac cone, as well as other parameters.