Pressure-Induced Superconductivity In Parent Cafeasf Single Crystals

Flouroarsenide CaFeAsF is a parent compound of the 1111 type of iron-based superconductors. It is similar to the parent LaFeAsO, but it is oxygen-free. To date, studies of pressure-induced effects have only focused on pure and doped polycrystalline CaFeAsF samples. Here, we carried out high-pressure electrical resistivity and Hall coefficient measurements up to 48.2 GPa on single crystals of CaFeAsF. The structural transition temperature T-str decreased monotonically upon increasing the pressure, and reached similar to 60K at 9.6 GPa. Superconductivity emerged suddenly at 8.6 GPa with the T-c,T-onset similar to 25.7K, which decreased monotonically with increasing pressure to 5.7 K under 48.2 GPa. Moreover, just after the appearance of superconductivity, the Hall coefficient at 40 K started to decrease with increasing pressure, while keeping its sign negative persisting up to 48.2 GPa.