Chirality reversal at finite magnetic impurity strength and local signatures of a topological phase transition

In this theoretical work we study spinless electrons hopping on the honeycomb lattice with a single magnetic impurity. The impurity generates orbital magnetization for the electrons. However, by computing two experimentally relevant observables (orbital magnetization via local marker and low energy currents) we find that the electronic orbital magnetization reverses at a critical impurity strength h_c. Correspondingly, the Chern number of an impurity superlattice also flips at h_c. Such a surprising chirality reversal was recently argued to arise from a putative tri-critical point of Dirac fermions at zero defect density. Our analysis of the single impurity finds that its T-matrix resonance which produces the global chirality reversal also leads to a reversal of currents in the defect core, suggesting a role of the defect structure at the h_c critical point of Dirac fermions with dilute impurities.