Observation of Fermi-energy dependent unitary impurity resonances in a strong topological insulator Bi2Se3 with scanning tunneling spectroscopy

TL;DR

This study uses scanning tunneling spectroscopy to investigate how impurity resonances in Bi2Se3 topological insulators depend on Fermi energy, revealing robust surface states and energy-dependent impurity effects.

Contribution

It demonstrates the Fermi-energy dependence of impurity resonances and confirms the robustness of topological surface states against non-magnetic impurities.

Findings

Impurity resonances diverge as Fermi level approaches Dirac point.

Surface state recovers within ~2 Å from impurities.

Topological protection persists despite high impurity density.

Abstract

Scanning tunneling spectroscopic studies of Bi2Se3 epitaxial films on Si (111) substrates reveal highly localized unitary impurity resonances associated with non-magnetic quantum impurities. The strength of the resonances depends on the energy difference between the Fermi level ({E_F}) and the Dirac point ({E_D}) and diverges as {E_F} approaches {E_D}. The Dirac-cone surface state of the host recovers within ~ 2{\AA} spatial distance from impurities, suggesting robust topological protection of the surface state of topological insulators against high-density impurities that preserve time reversal symmetry.