Concurrent Onset of Anomalous Hall Insulating state and Multifractal Wavefunction Structure in a Ferromagnetic Nodal Line Semimetal

Dirac nodes are prevalent in topological states of matter either in their boundary states, as in topological insulators, or in the bulk, as in topological semimetals. Gapping out those Dirac nodes gives rise to higher-order topological states of matter and exotic responses such as the anomalous quantum Hall effect and chiral anomaly. Here we demonstrate an alternative route for the realization of anomalous Hall insulators by gapping the nodal line band crossing in the ferromagnetic topological semimetal Fe3GeTe2 with disorder and electronic interactions. We find the simultaneous onset of diverse phenomenology below a common temperature scale of about 10K: a metal-to-insulator crossover in longitudinal resistivity; plateauing of the anomalous Hall conductivity; Formation of a sharp zero bias dip in local scanning tunneling spectroscopy; evolution of a multifractal structure of the surface electronic wavefunction. These concurrent observations suggest that when strong electronic interactions are present, the disorder can robustly promote the realization of topological responses rather than hamper their formation which commonly occurs in the non-interacting case.