Common Origin of the Circular-dichroism Pattern in ARPES of SrTiO3 and CuxBi2Se3

TL;DR

This paper investigates circular dichroism in photoelectron angular distributions of SrTiO3:Nb and CuxBi2Se3 using laser ARPES, revealing new symmetry nodes and the momentum-dependent penetration depth of topological states.

Contribution

It uncovers a new type of symmetry node in CDAD related to the crystal's mirror planes and electronic dimensionality, providing a unified explanation for observed patterns.

Findings

Identification of a new symmetry node in CDAD when the mirror plane is vertical to the incidence plane.

Explanation of flower-shaped CDAD patterns around the Fermi level and Dirac point.

Demonstration that the penetration depth of topological states varies with momentum.

Abstract

Circular dichroism in the angular distribution (CDAD) of photoelectrons from SrTiO3:Nb and CuxBi2Se3 is investigated by 7-eV laser ARPES. In addition to the well-known node that occurs in CDAD when the incidence plane matches the mirror plane of the crystal, we show that another type of node occurs when the mirror plane of the crystal is vertical to the incidence plane and the electronic state is two dimensional. The flower-shaped CDAD's occurring around the Fermi level of SrTiO3:Nb and around the Dirac point of CuxBi2Se3 are explained on equal footings. We point out that the penetration depth of the topological states of CuxBi2Se3 depends on momentum.