AVS 64th International Symposium & Exhibition
    Magnetic Interfaces and Nanostructures Division Monday Sessions
       Session MI+BI+EM+SA-MoA

Paper MI+BI+EM+SA-MoA3
Enantio-sensitive Charge Transfer in Adsorbed Chiral Molecules Probed with X Ray Circular Dichroism

Monday, October 30, 2017, 2:20 pm, Room 11

Session: Role of Chirality in Spin Transport and Magnetism
Presenter: Juan José de Miguel, Universidad Autónoma de Madrid, Spain
Authors: F.J. Luque, Universidad Autónoma de Madrid, Spain
I.A. Kowalik, Polish Academy of Sciences, Poland
M.Á. Niño, IMDEA-Nanoscience, Spain
D. Arvanitis, Uppsala University, Sweden
J.J. de Miguel, Universidad Autónoma de Madrid, Spain
Correspondent: Click to Email
Recent studies have shown how layers of purely organic, chiral molecules can induce the appearance of strong spin polarization in initially unpolarized electron currents. [1] Furthermore, spin-polarized photoemission experiments comparing adsorbed films of opposite enantiomers of the same chiral molecule have revealed that they can display different behavior, producing spin polarization along different directions in space instead of simply changing its sign. [2]

In this study enantio-pure ultrathin films of chiral 1,2-diphenyl-1,2-ethanediol (DPED) have been deposited on Cu(100) at 100 K and studied at the MAX-lab synchrotron in Lund, Sweden, using circularly polarized x ray absorption (XAS) at the carbon K edge. XAS excites element-specific core electrons to empty levels in the ground state thus probing the molecule's electronic configuration. The different features present in the absorption spectra have been identified and assigned to specific electronic transitions. The comparison of absorption spectra taken with photons of opposite helicity shows a surprisingly strong dichroism localized at transitions into empty molecular orbitals with π character. Theoretical modeling of the spectra reveals that this response is associated to the charge transferred between the Cu substrate and the adsorbed molecules. This charge is found to be polarized in orbital momentum, and the direction of the polarization is different for the two enantiomers studied: (R,R)–DPED and (S,S)–DPED. These findings indicate that chiral organic layers can play an important role in the emerging field of molecular orbitronics.

[1] B. Göhler V. Hamelbeck, T. Z. Markus, M. Kettner, G. F. Hanne, Z. Vager, R. Naaman, and H. Zacharias, Science 331, 894 (2011).

[2] M. Á. Niño, I. A. Kowalik, F. J. Luque, D. Arvanitis, R. Miranda, and J. J. de Miguel, Adv. Mater. 26, 7474 (2014).