Spin and Charge Structure of the Surface States in Topological Insulators

TL;DR

This paper analyzes the spin and charge distributions of surface states in 3D topological insulators, revealing complex spin structures on various surfaces and how interface orientation affects the Dirac point and surface charge distribution.

Contribution

It provides a detailed theoretical study of the spin and charge structures on different crystal surfaces of topological insulators, including effects of sublattice contributions and interface orientation.

Findings

Complex spin structures on non-(111) surfaces due to sublattice contributions.

Surface Dirac crossing position depends on interface orientation.

Surface charge redistribution occurs at edges between different facets.

Abstract

We investigate the spin and charge densities of surface states of the three-dimensional topological insulator $Bi_2Se_3$, starting from the continuum description of the material [Zhang {\em et al.}, Nat. Phys. 5, 438 (2009)]. The spin structure on surfaces other than the 111 surface has additional complexity because of a misalignment of the contributions coming from the two sublattices of the crystal. For these surfaces we expect new features to be seen in the spin-resolved ARPES experiments, caused by a non-helical spin-polarization of electrons at the individual sublattices as well as by the interference of the electron waves emitted coherently from two sublattices. We also show that the position of the Dirac crossing in spectrum of surface states depends on the orientation of the interface. This leads to contact potentials and surface charge redistribution at edges between different facets of the crystal.