Photoelectron Holography Study of La(O,F)BiS₂

We performed photoelectron and Auger-electron holography to study the local structure of La(O,F)BiS2. We found that the previously reported surface-dominant Bi 4f component exhibits a hologram pattern derived from the forward focusing peaks. This provides spectroscopic evidence of the existence of two bulk Bi chemical sites. A comparison of the experimental holograms with the simulated holograms using the tetragonal and charge density wave (CDW) models, as well as with a monoclinic structure model proposed for the high-pressure phase exhibiting the highest superconducting transition temperature among BiS2-based superconductors, showed that the monoclinic structure model does not reproduce the experimental hologram. This suggests that it may not be a dominant local structure for as-grown La(O,F)BiS2. The experimental hologram of the F KLL Auger electron is similar to that of the O KLL, providing direct evidence that F atoms are incorporated into the O sites. These results are valuable for understanding the physical properties of La(O,F)BiS2.