Tight-binding approach to understand photoelectron intensity from graphene for circularly polarized light

TL;DR

This study uses a tight-binding model to analyze how imperfect circular polarization affects photoelectron intensity and circular dichroism in graphene's angle-resolved photoemission spectroscopy, emphasizing the importance of experimental conditions.

Contribution

It reveals how polarization imperfections induce circular dichroism in graphene photoemission, highlighting an additional factor influencing experimental observations.

Findings

Perfect circular polarization yields identical intensity distributions for left and right polarization.

Imperfections in polarization induce circular dichroism in photoelectron signals.

The degree of dichroism increases with polarization imperfection.

Abstract

We have investigated the effect of imperfect circular polarization on the angle-resolved photoemission spectroscopy signal, using graphene as a prototypical system that can be understood within tight-binding formalism. We found that perfect left- and right-circularly polarized lights give the same photoelectron intensity distribution around a constant energy contour of the graphene $\pi$ band. On the other hand, upon breaking the purity of the polarization, photoelectron intensity starts to show circular dichroism, which is enhanced with further increasing the imperfection. Our results predict the existence of an additional factor for the circular dichroism observed in the photoemission signal from graphene and hence suggest the importance of experimental conditions to understand circular dichroism observed via photoemission spectroscopy.