Electronic band structure and Fermi surface for new layered superconductor LaO$_{0.5}$F$_{0.5}$BiS$_2$ in comparison with parent phase LaOFBiS$_2$ from first principles

By means of first-principles calculations, we have probed the peculiarities of the electronic band structure and Fermi surface for the recently discovered layered superconductor LaO$_{0.5}$F$_{0.5}$BiS$_2$ in comparison with the parent phase LaOBiS$_2$. The electronic factors promoting the transition of LaOBiS$_2$ upon fluorine doping to superconducting state: inter-layer charge transfer, the evolution of the Fermi surface, and the dependence of the near-Fermi densities of states on $x$ for LaO$_{1-x}$F$_x$BiS$_2$ are evaluated and discussed in comparison with the available experiments.