Disentangling surface and bulk photoemission using circularly polarized light

TL;DR

This paper demonstrates how circularly polarized light in ARPES can differentiate between surface and bulk electronic states by exploiting near-surface fields and dielectric discontinuities.

Contribution

It introduces a method to disentangle surface and bulk emissions in ARPES using circular dichroism caused by near-surface fields.

Findings

Circular dichroism is significant within the first unit cell.

The method distinguishes surface-related and bulk components in ARPES spectra.

Application to YBa2Cu3O7−δ shows effective separation of surface and bulk signals.

Abstract

We show that in the angle resolved photoemission spectroscopy (ARPES) near-surface induced fields can be useful for disentangling the surface and bulk related emission. The jump of the dielectric function at the interface results in a nonzero term $\operatorname{div}\textbf{A}$ in the photoemission matrix element. The term happens to be significant approximately within the first unit cell and leads to the circular dichroism for the states localized therein. As an example we use ARPES spectra of an YBa$_2$Cu$_3$O$_{7-\delta}$ crystal to distinguish between the overdoped surface related component and its bulk counterparts.