Disorder-induced coupling of Weyl nodes in WTe$_2$

The finite coupling between Weyl nodes due to residual disorder is investigated by magnetotransport studies in WTe$_2$. The anisotropic scattering of quasiparticles is evidenced from classical and quantum transport measurements. A new theoretical approach using a real band structure is developed to calculate the dependence of the scattering anisotropy with the correlation length of the disorder. A comparison between theory and experiments reveals for the first time a short correlation length in WTe$_2$ ($\xi$~nm). This result implies a significant coupling between Weyl nodes and other bands, so that inter-node scattering strongly reduces topologically non-trivial properties, such as the chiral anomaly.