Theory of quasiparticle interference on the surface of a strong topological insulator

TL;DR

This paper provides a theoretical analysis of quasiparticle interference patterns on the surface of strong topological insulators, highlighting unique features due to the helical liquid nature and confirming experimental observations of suppressed backscattering.

Contribution

It offers a comprehensive classification of interference patterns in helical liquids, predicting new magnetic impurity effects and confirming the absence of backscattering from non-magnetic impurities.

Findings

Confirmed absence of backscattering from non-magnetic impurities.

Predicted new interference features from magnetic impurities.

Classified universal interference patterns in helical liquids.

Abstract

Electrons on the surface of a strong topological insulator, such as Bi2Te3 or Bi1-xSnx, form a topologically protected helical liquid whose excitation spectrum contains an odd number of massless Dirac fermions. A theoretical survey and classification is given of the universal features, observable by the ordinary and spin-polarized scanning tunneling spectroscopy, in the interference patterns resulting from the quasiparticle scattering by magnetic and non-magnetic impurities in such a helical liquid. Our results confirm the absence of backscattering from non-magnetic impurities observed in recent experiments and predict new interference features, uniquely characteristic of the helical liquid, when the scatterers are magnetic.