Phase transitions and suppression of magnetoresistance in WTe2-xSesystem

X-ray diffraction, Raman spectroscopy, and electrical resistivity measurements on polycrystalline WTe2-xSe(0 ⩽ x ⩽ 0.8) reveal aT-1T'structural phase transition and suppression of magnetoresistance atx = 0.2. These phenomena are consistent with the pressure phase diagram of WTe₂. However, chemical pressure due to substitution of smaller Se ion cannot generate pressure required for the phase transition. Strain induced by sample inhomogeneity is believed to be a trigger to the behaviors. In agreement with previous predictions and reports, a mixed phase of1T'and 2Hstructures was also detected in Se-rich samples. Coincidentally atx = 0.2, electrical resistivity analysis suggests a phase transition from a metallic phase to a nonmetallic phase that is possibly a topological-insulating phase.