Crossover from Hole-To Electron-Dominant Regions in Iron-Chalcogenide Superconductors Induced by Te/Se Substitution

We have investigated a Te/Se substitution effect on the field dependence of Hall resistivity in FeSe1-xTex (x = 0.5-0.7) thin films grown on LaAlO3 and CaF2 substrates. By observing the magnetic field dependence of Hall resistivity, the crossover from hole- to electron-dominant regions is observed to occur between x = 0.5 and 0.6 in the films on LaAlO3, while no such crossover is observed in those on CaF2. The results indicate that the substitution of Te for Se effectively acts as electron doping, while the lattice strain also has an additional effect on the balance of hole and electron densities. These two factors can be independently used to optimize superconducting transition temperature so as to tune the doping level near the boundary where the hole density becomes equal to the electron density. (c) 2015 The Japan Society of Applied Physics