Proximity to Fermi-surface topological change in superconducting   LaO0.54F0.46BiS2
  The electronic structure of nearly optimally-doped novel superconductor LaO$_{1-x}$F$_x$BiS$_2$ (${\it x}$ = 0.46) was investigated using angle-resolved photoemission spectroscopy (ARPES). We clearly observed band dispersions from 2 to 6 eV binding energy and near the Fermi level (${\it E}_{\rm F}$), which are well reproduced by first principles calculations when the spin-orbit coupling is taken into account. The ARPES intensity map near ${\it E}_{\rm F}$ shows a square-like distribution around the $\Gamma$(Z) point in addition to electronlike Fermi surface (FS) sheets around the X(R) point, indicating that FS of LaO$_{0.54}$F$_{0.46}$BiS$_2$ is in close proximity to the theoretically-predicted topological change. 
K. Terashima, J. Sonoyama, T. Wakita, M. Sunagawa, K. Ono, H.   Kumigashira, T. Muro, M. Nagao, S. Watauchi, I. Tanaka, H. O...
cond-mat.supr-con cond-mat.mtrl-sci