Transport properties of LaFeP$_{1-x}$As$_{x}$O$_{1-y}$F$_{y}$: Evidence for two superconducting states

Resistivity and Hall coefficient of polycrystalline LaFeP$_{1-x}$As$_{x}$O$_{1-y}$F$_{y}$ with $x$ = 0 -- 1.0 and $y$ = 0 -- 0.1 have been investigated. In the $T_{c}$-$x$ phase diagram for F-free ($y$ = 0) samples, two superconducting domes have been revealed at $x$ = 0 -- 0.3 ($T_{c}^{max}$ $\sim $12 K) and 0.6 -- 0.8 ($T_{c}^{max}$ $\sim $10 K). Hall effect measurements suggest that the electronic states in these two dome regions are different from each other. For $y$ = 0.05, double peaks of $T_{c}$ are observed at $x$ $\sim $ 0.4 and 0.8, while only one dome with $T_{c}^{max}$ $\sim$28 K is observed for $y$ = 0.1 [1]. These changes can be regarded as the fusion of two $T_{c}$ domes upon F doping. \\[4pt] [1] S. Miyasaka et al., to be published in J. Phys. Soc. Jpn. (arXiv:1310.2731).