Phase transitions and suppression of magnetoresistance in WTe 2−x Se x system

Abstract

Abstract X-ray diffraction, Raman spectroscopy, and electrical resistivity measurements on polycrystalline WTe 2 − x Se x ( 0   ⩽   x   ⩽   0.8 ) reveal a T d - 1 T ′ structural phase transition and suppression of magnetoresistance at x = 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 of 1 T ′ and 2H structures was also detected in Se-rich samples. Coincidentally at x = 0.2, electrical resistivity analysis suggests a phase transition from a metallic phase to a nonmetallic phase that is possibly a topological-insulating phase.