Rabin Dahal

First Prize; Advisor: C. W. Chu Ph.D. student in Physics; "Pressure-Induced Superconductivity & Doping-Tunable Structural Transition in Weyl Semimetal Mo1-xWxTe2"


Abstract: Transition metal dichalcogenides Mo1-xWxTe2 have generated much interest due to their reported topological properties and because their parent compounds, MoTe2 and WTe2, are reported to exhibit the Weyl semimetal state, large unsaturated magnetoresistance, and superconductivity. In addition, Mo0.25W0.75Te2 has been confirmed to be a Weyl semimetal and should be tunable across the phase diagram. High-quality single crystals of MoTe2 and WTe2 were grown by flux method and Mo1- xWxTe2 (x = 0.10, 0.30, 0.40, 0.50, 0.70, 0.75, and 0.90) were grown via chemical vapor transport method. Resistivity measurements up to 650 K were conducted using a home-made high-temperature resistivity probe and high-pressure measurements up to 17 kbar were performed using a BeCu clamp cell for selected doping compositions. With increasing W concentration, the structural transition temperature increased and was also suppressed under pressure. No superconductivity was observed in Mo0.25W0.75Te2 down to 1.3 K or under pressure up to 17 kbar. However, superconductivity was induced in Mo0.60W0.40Te2 with an onset Tc of 1.7 K under 8.4 kbar and in Mo0.90W0.10Te2 with an onset Tc of 1.4 K under 3.9 kbar. As the Tc continuously increased with pressure for all samples, additional diamond anvil cell measurements are planned to explore pressure effects further.