Magnetotransport across Weyl semimetal grain boundaries

A clean interface between two Weyl semimetals features a universal, field-linear tunnel magnetoconductance of $(e^2/h)N_\mathrm{ho}$ per magnetic flux quantum, where $N_\mathrm{ho}$ is the number of chirality-preserving topological interface Fermi arcs. In this work we show that the linearity of the magnetoconductance is robust with to interface disorder. The slope of the magnetoconductance changes at a characteristic field strength $B_\mathrm{arc}$ -- the field strength for which the time taken to traverse the Fermi arc due to the Lorentz force is equal to the mean inter-arc scattering time. For fields much larger than $B_\mathrm{arc}$, the magnetoconductance is unaffected by disorder. For fields much smaller than $B_\mathrm{arc}$, the slope is no longer determined by $N_\mathrm{ho}$ but by the simple fraction $N_\mathrm{L} N_\mathrm{R}/(N_\mathrm{L}+N_\mathrm{R})$, where $N_\mathrm{L}$ and $N_\mathrm{R}$ are the numbers of Weyl-node pairs in the left and right Weyl semimetal, respectively. We also consider the effect of spatially correlated disorder potentials, where we find that $B_\mathrm{arc}$ decreases exponentially with increasing correlation length. Our results provide a possible explanation for the recently observed robustness of the negative linear magnetoresistance in grained Weyl semimetals.