Importance of substrate spin-orbit coupling in layers of chiral organic molecules on metal surfaces, and the origin of the CISS effect

A great deal of attention is being devoted to the study of the CISS (Chiral-Induced Spin Selectivity) effect, which describes the appearance of spin polarization in electrons transmitted through homochiral media in absence of magnetic elements. This phenomenon has already been confirmed by a multitude of experimental observations and can revolutionize fields such as molecular spintronics or pharmacology, by providing means to separate enantiomers for biological or medical use. Nevertheless, a satisfactory theoretical understanding has not yet been reached, and there exists considerable debate regarding the role and magnitude of the spin-orbit coupling (SOC) in these systems and its importance in achieving the observed spin polarization. 
We propose to carry out a systematic analysis of the effects of SOC strength by using X ray circular dichroism in absorption to study the induced magnetic moments appearing in layers of homochiral organic molecules adsorbed on Al(111), Cu(111) and Au(111) metal surfaces, resolving separately the orbital and spin contributions. These substrates feature amply different SOCs, and the deposited chiral organic compounds, methylbenzylamine and diphenylethylenediamine, have different but closely related configurations possessing 1 and 2 chiral centers respectively. With these experiments we expect to identify relevant trends and shed light on the fundamental origin of this suggestive effect.