Electronic tunability in crystals with weakly bound layers can be achieved through layer stacking order. One such example is ${\mathrm{MoTe}}_2$, where the low-temperature orthorhombic $T_d$ phase is topological and host to Weyl quasiparticles. The transition mechanism to the nontrivial topology is elucidated by single-crystal neutron diffraction. Upon cooling from the monoclinic $1T^{\prime }$ to the $T_d$ phase, diffuse scattering accompanies the transition, arising from random, in-plane layer displacements, and dissipates upon entering the $T_d$ phase. Diffuse scattering is observed only in the $H0L$ plane due to irreversible layer shifts along the $c$ axis that break the centrosymmetry of the monoclinic lattice.

• Received 26 July 2018

DOI:https://doi.org/10.1103/PhysRevB.99.161105