2009 年 19 巻 4 号 p. 202-206
Crystal structures of iron-based superconductors are introduced. Powder neutron diffraction measurements reveal that their crystal structure and superconductivity are strongly correlated. Superconducting transition temperature (Tc) attains a maximum value when FeAs4 or Fe(Se,Te)4-Tetrahedrons form a regular shape. Based on this relationship, we have performed high-pressure resistivity experiments on FeSe0.5Te0.5, which has the simplest crystal structure in iron-based superconductors. Tc increased rapidly from 14 K to 26 K upon applying pressure up to 2 GPa and we clarified the pressure-induced phase transition from superconducting to metallic phase on the P-Tc phase diagram for the first time.
