Disordered double Weyl node

Double Weyl nodes are topologically protected band crossing points which carry chiral charge $\pm2$. They are stabilized by $C_4$ point group symmetry and are predicted to occur in $\mathrm{SrSi_2}$ or $\mathrm{HgCr_{2}Se_{4}}$. We study their fate in the presence of quenched disorder by numerical transport calculations and scaling arguments. We find that a double Weyl node is unstable in a disordered environment and splits into a pair of emergent simple Weyl nodes which carry equal chiral charge of $\pm1$. This pair of simple Weyl nodes is robust to disorder up to a certain critical disorder strength, in complete analogy to their `elementary' counterparts.