Abstract
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.
Highlights
In Weyl and Dirac semimetals, bulk gapless excitations are described by a Dirac equation, with a linear band dispersion and a crossing at a band degeneracy point close to the Fermi energy
Contrary to Dirac semimetals, for which high-symmetry Dirac points always give pairs of Fermions with opposite chiralities, the inversion symmetry breaking in Weyl semimetals splits the position of band degeneracy points in the reciprocal space into two distinct Weyl nodes
Besides the manifestation of a chiral anomaly [7,8], this implies the presence of electron and hole pockets that touch each other when the Fermi energy is at the Weyl node
Summary
In Weyl and Dirac semimetals, bulk gapless excitations are described by a Dirac equation, with a linear band dispersion and a crossing at a band degeneracy point close to the Fermi energy. A comparison with a theoretical model that considers scattering processes within the specific band structure of WTe2, using a renormalization method, allows us to infer a rather short ξ (∼5 nm) of the disorder. This disorder leads to a finite coupling between Weyl nodes that can suppress the transport properties related to the topology of the band structure. A particle can be scattered from a Weyl cone to another band due to the presence of impurities This effect is related to the strength of the disorder (δV in Fig. 1) and to 1/ξ , which defines the range of the scattering in reciprocal space. Our theoretical approach based on a material specific band structure (including the spin texture) establishes the correspondence between τtr/τQ, k for holes and ξ in a disordered material and, gives a quantitative estimation of ξ
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