Valence Band Circular Dichroism in non-magnetic Ag/Ru(0001) at normal emission

TL;DR

This study observes significant valence band circular dichroism in non-magnetic Ag/Ru(0001) systems at normal emission, revealing how dichroism varies with film thickness and symmetry effects.

Contribution

It reports the first measurement of valence band circular dichroism in non-magnetic Ag/Ru(0001) at normal emission, highlighting the role of symmetry lowering.

Findings

Circular dichroism exceeds 6% for a single Ag layer.

Dichroism decreases with increasing Ag film thickness.

Symmetry lowering influences dichroism even at normal emission.

Abstract

For the non-magnetic system of Ag films on Ru(0001), we have measured the circular dichroism of photoelectrons emitted along the surface normal, the geometry typically used in photoemission electron microscopy (PEEM). Photoemission spectra were acquired from micrometer-sized regions having uniformly thick Ag films on a single, atomically flat Ru terrace. For a single Ag layer, we find a circular dichroism that exceeds 6% at the d-derived band region around 4.5 eV binding energy. The dichroism decreases as the Ag film thickness increases to three atomic layers. We discuss the origin of the circular dichroism in terms of the symmetry lowering that can occur even in normal emission.