Superconductivity in Weyl semimetal Mo_xW_1-xTe₂ driven by high pressure

Tungsten ditelluride and molybdenum ditelluride have attracted tremendous attention due to recent discoveries of the Weyl semimetal state, large unsaturated magnetoresistance, and superconductivity in these materials. Mo_xW_1-xTe₂ is reported to be a Weyl semimetal with x = 0.25 and Weyl semimetal states are also predicted to exist in other doping. We carried out systematic high pressure measurements on Mo_xW_1-xTe₂ single crystals with doping via homemade BeCu clamp cells. High-quality single crystals of Mo_xW_1-xTe₂, with x = 0.25, 0.60, 0.90, were grown by chemical vapor transport method which were then characterized by X-ray diffraction and energy dispersive X-ray spectroscopy. In Mo_0.25W_0.75Te₂, a structural transition was observed under pressure 12.3 kbar with no signature of superconductivity at temperature down to 1.3 K and under pressure up to 17 kbar. In Mo_0.60W_0.40Te₂ and Mo_0.90W_0.10Te₂, structural transitions were observed at ambient pressure. Superconductivity appears in Mo_0.60W_0.40Te₂ with an onset T_c of 1.7 K under 8.4 kbar and in Mo_0.90W_0.10Te₂ with an onset T_c of 1.4 K under 3.9 kbar. T_c continuously increases as pressure increases up to 17 kbar, the highest pressure we applied. Measurements under higher pressure range using diamond anvil cells are in progress.