Absence of localization in a class of topological systems

Topological matter is a trending topic in condensed matter: From a fundamental point of view, it has introduced new phenomena and tools and, for technological applications, it holds the promise of basic stable quantum computing. Similarly, the physics of localization by disorder, an old paradigm of obvious technological importance in the field, continues to reveal surprises when new properties of matter appear. This work deals with the localization behavior of electronic systems based on partite lattices, with special attention to the role of topology. We find an unexpected result from the point of view of localization properties: A robust topological metallic state characterized by a nonquantized Hall conductivity arises from strong disorder in topological systems based on bipartite lattices. The key issue is the nature of the disorder realization: selective disorder in only one sublattice. The generality of the result is based on the partite nature of most recent two-dimensional materials such as graphene or transition-metal dichalcogenides, and the possibility of the physical realization of the particular disorder demonstrated in Ugeda et al. [M. M. Ugeda et al., Phys. Rev. Lett. 104, 096804 (2010)] and Zhao et al. [L. Zhao et al., Science 333, 999 (2011)].
E.C. acknowledges the financial support of FCT-Portugal through Grant No. EXPL/FISNAN/1728/2013. This research was supported in part by the Spanish MECD Grant No. FIS2014-57432-P, the European Union structural funds, and the Comunidad de Madrid MAD2D-CM Program (S2013/MIT-3007), as well as the European Union Seventh Framework Programme under Grant Agreement No. 604391 Graphene Flagship FPA2012-32828. S2013/MIT-3007/MAD2D-CM info:eu-repo/grantAgreement/EC/FP7/604391