Quasiparticle band structure of the almost-gapless transition-metal-based Heusler semiconductors

Transition-metal-based Heusler semiconductors are promising materials for a variety of applications ranging from spintronics to thermoelectricity. Employing the $GW$ approximation within the framework of the FLAPW method, we study the quasiparticle band structure of a number of such compounds being almost gapless semiconductors. We find that in contrast to the $sp$-electron based semiconductors such as Si and GaAs, in these systems, the many-body corrections have a minimal effect on the electronic band structure and the energy band gap increases by less than 0.2 eV, which makes the starting point density functional theory (DFT) a good approximation for the description of electronic and optical properties of these materials. Furthermore, the band gap can be tuned either by the variation of the lattice parameter or by the substitution of the $sp$-chemical element.

Figure 1

Convergence of the energy band gap with the number of bands and the $\mathbf{k}$-point grid for (CoFe)TiAl.

Figure 2

Calculated electronic band structure of (CoFe)TiAl along the high-symmetry directions in the first Brillouin zone using either the PBE-GGA (red dashed line) or the $GW$ (blue solid line) approximations.

Figure 3

Energy band-gap tuning with the variation of the lattice parameter for the compounds (FeMn)TiP and (CoCr)TiP using the $GW$ approximation.