Observation of a Topological Insulator Dirac Cone Reshaped by Non-magnetic Impurity Resonance

The helical Dirac cone states on the surface of topological insulator (TI) are thought to be insensitive to weak, non-magnetic disorder. Recently, theoretical modeling has shown that, without violating the time reversal symmetry, randomly distributed point defects/impurities of a crystal lattice can give rise to resonance states that greatly change the Dirac surface state dispersions and the physical nature of the low-energy quasiparticles. In this talk, I will present our linear dichroic angular resolved photoemission spectroscopy (LD-ARPES) study on disorder-enriched Bi₂Se₃. The LD-ARPES spectra reveal a large anomalous kink-like feature in the Dirac cone dispersion, which matches the predicted signature of coherent hybridization with an impurity resonance. The dispersion anomaly is found to be associated with a DOS peak, and both features are progressively attenuated when successive low temperature annealing is applied to reduce disorder. The experimental observation of these features, which closely resemble theoretical predictions, clarifies the interplay between a topological Dirac cone and the point-defect disorder common in applied systems.