Evolution of the Fermi surface in superconductor ${\mathrm{PrO}}_{1-x}{\mathrm{F}}_x{\mathrm{BiS}}_2$ ($x=0.0,0.3,$ and 0.5) revealed by angle-resolved photoemission spectroscopy

We have investigated the electronic structure evolution with F doping in $\mathrm{Pr}{\mathrm{O}}_{1-x}{\mathrm{F}}_x\mathrm{Bi}{\mathrm{S}}_2$ ($x=0.0,0.3,0.5$) by means of angle-resolved photoemission spectroscopy. Undoped $\mathrm{Pr}\mathrm{O}\mathrm{Bi}{\mathrm{S}}_2$ exhibits Fermi surface (FS) pockets around the $X$ point which can be associated with electron doping due to the ${\mathrm{Pr}}^{3+}/{\mathrm{Pr}}^{4+}$ mixed valence. At $x=0.3$, the FS pockets are expanded, and their area is almost consistent with the F doping level. Interestingly, horizontal segments facing each other in the rectangular FS pockets lose their spectral weight. The partial suppression of the FS pockets suggests possible anisotropic charge fluctuations around $x=0.3$. At $x=0.5$, the FS area is much smaller than the expected value as commonly observed for $\mathrm{Ce}{\mathrm{O}}_{0.5}{\mathrm{F}}_{0.5}\mathrm{Bi}{\mathrm{S}}_2$ and $\mathrm{Nd}{\mathrm{O}}_{0.5}{\mathrm{F}}_{0.5}\mathrm{Bi}{\mathrm{S}}_2$. In addition, the highly depleted spectral weight at the FS pockets would be consistent with evident charge fluctuations driven by atomic disorder in the $\mathrm{Bi}{\mathrm{S}}_2$ network.

Figure 1

(a) Crystal structure of $\mathrm{Pr}\mathrm{O}\mathrm{Bi}{\mathrm{S}}_2$ created by vesta [21]. (b) Two-dimensional Brillouin zone of $\mathrm{Pr}{\mathrm{O}}_{1-x}{\mathrm{F}}_x\mathrm{Bi}{\mathrm{S}}_2$.

Figure 2

Top: Fermi surface map for $\mathrm{Pr}{\mathrm{O}}_{1-x}{\mathrm{F}}_x\mathrm{Bi}{\mathrm{S}}_2$ ($x=0.0$). Bottom: Band map along the $\mathrm{\Gamma }-X$ cut.

Figure 3

Top: Fermi surface map for $\mathrm{Pr}{\mathrm{O}}_{1-x}{\mathrm{F}}_x\mathrm{Bi}{\mathrm{S}}_2$ ($x=0.3$). The solid circles indicate the Fermi surface points deduced from momentum distribution curves along the horizontal cuts. The open circles indicate the valence band top points deduced from momentum distribution curves along the vertical cuts. The solid curves indicate calculated Fermi surfaces for 0.3 electron per Bi. Bottom: Band maps along cuts 1, 2, 3, and 4 in the Fermi surface map. The dotted curves indicate calculated band dispersions for 0.3 electron per Bi.

Figure 4

Top: Fermi surface map for $\mathrm{Pr}{\mathrm{O}}_{1-x}{\mathrm{F}}_x\mathrm{Bi}{\mathrm{S}}_2$ ($x=0.5$). The solid circles indicate the Fermi surface points deduced from momentum distribution curves along the horizontal and vertical cuts. The open squares indicate the Fermi surface points for $x=0.3$. Bottom: Band maps along cuts 1, 2, 3, and 4 in the Fermi surface map.