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

TL;DR

This study reports the first direct observation of impurity-induced reshaping of the Dirac cone in a topological insulator, revealing a kink-like dispersion caused by non-magnetic impurity resonance, with implications for surface state properties.

Contribution

It provides experimental evidence of impurity resonance effects on topological insulator surface states, confirming theoretical predictions about Dirac cone distortion by non-magnetic impurities.

Findings

Observation of a kink-like dispersion in the Dirac cone

Correlation between impurity resonance and dispersion anomaly

Implications for topological surface state robustness

Abstract

The massless Dirac electrons found at topological insulator surfaces are thought to be influenced very little by weak, non-magnetic disorder. However, a resonance effect of strongly perturbing non-magnetic impurities has been theoretically predicted to change the dispersion and physical nature of low-energy quasiparticles, resulting in unique particle-like states that lack microscopic translational symmetry. Here we report the direct observation of impurities reshaping the surface Dirac cone of the model 3D topological insulator Bi2Se3. For the first time, a pronounced kink-like dispersion feature is observed in disorder-enriched samples, and found to be closely associated with the anomaly caused by impurity resonance in the surface state density of states, as observed by dichroic angle resolved photoemission spectroscopy (ARPES). The experimental observation of these features, which closely resemble theoretical predictions, has significant implications for the properties of topological Dirac cones in applied scenarios that commonly feature point defect disorder at surfaces or interfaces.