Electronic structure of low-carrierYb4As3and related compounds

The electronic structure of the heavy-fermion compound ${\mathrm{Yb}}_4{\mathrm{As}}_3$ is investigated using energy band calculations within the so-called local spin density $\mathrm{approximation}+U$ approach. We find as a generic feature a very rigid pinning of the energy of Yb $4f$ hole states close to the top of the pnictide $p$ band and the Fermi level pinned to those hole states, providing for a very low-carrier concentration. Calculated Fermi surface and optical properties compare well with experimental data. We also present electronic structure results for the related compounds ${\mathrm{Yb}}_4{\mathrm{P}}_3,{\mathrm{Yb}}_4{\mathrm{Sb}}_3,{\mathrm{Yb}}_4{\mathrm{Bi}}_3,$ and ${\mathrm{Yb}}_4{(\mathrm{P}}_{0.5}{\mathrm{As}}_{0.5}{)}_3.$