Disorder and the 1T'-T_d structural phase transition in MoTe₂

The transition metal dichalcogenide MoTe₂ has been much studied recently due to a reported Weyl semimetal state in its low-temperature T_d phase and very large magnetoresistance which onsets at low temperatures, but the structural transition, consisting of shifts of layers along a crystallographic axis in the 1T' phase relative to the T_d phase, has not received much experimental study since these phases were first reported several decades ago. We study the 1T'-T_d transition in MoTe₂ via single crystal neutron diffraction. In the vicinity of the transition, diffuse scattering rods are seen, indicating disorder in the displacement of layers along the shear direction. We determine the amount and kind of disorder by comparison with calculations, and discuss the nature of the structural phase transition in light of this disorder.