Absence of localization in Weyl semimetals

One of the fundamental facts of condensed matter physics is that sufficient amount of disorder always turns a Fermi liquid metal into an Anderson insulator: a compressible, but

non-conducting phase of matter. Recently, topological semimetals have emerged as another way a metallic phase may be realized. In this paper we point out that, unlike ordinary metals, at least some topological semimetals are immune to localization, as long as their topological response is kept fixed. We present several physical arguments, based on decorated domain wall constructions, as well as Keldysh nonlinear sigma model, to back up this claim.