Superconducting phase diagram of single crystal Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ (0.5$\le $x$\le $1.0)

Among other iron pnictides, Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ is unique regarding the persistence of superconductivity in this compound up to the end member KFe$_{2}$As$_{2}$. Interestingly, the SC gap is changed with hole doping from fully opened gaps near the optimally doped region ($x=$0.4) to nodal gaps at the end member, KFe$_{2}$As$_{2}$. From these results, it is expected to show two-dome structure in superconducting phase diagram. However, it has not been clarified whether two-dome structure is seen or not because there are only a few repots on the phase diagram from optimally doped region to the end member. In this study, we report the result of the phase diagram of Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ using the single crystals. The single crystals were synthesized by self-flux method and we succeeded in growing single crystalline samples from 0.5 to 1.0. The superconducting transition temperature ( $T_{\mathrm{c}}$ ) was determined by SQUID measurement. As increasing K concentration $x$, $T_{\mathrm{c}}$ did not follow the linear relation around $x=$0.7. The result suggests that this compound may have two-dome structure.