Chirality Induced spin selectivity in electron transmission through self assembled monolayers of biomolecules

Abstract: ‘Chirality’ in molecular systems represents structural asymmetry in which one enantiomer has “right handed” symmetry and the other “left handed”. The interaction of circularly polarized light, magnetic field or spin-polarized electrons with chiral potential varies for the specific enantiomer. Indeed it was found that the transmission of electrons through chiral system yieldsspin polarized electron due to the lack of inversion symmetry of chiral molecules. I will present the discovery and development of chiral induced spin filtering effect of self-assembled monolayers made from molecules having a helical structure, like protein (bacteriorhodopsin), ds DNA and oligopeptides of different molecular length adsorbed on Au, Ni and Al thin films. Our results indicate that helical structure promotes electron transmission and efficient spin filtering. Polarization modulated IR spectroscopy and circular dichroism spectroscopic measurements confirm that there is a correlation between the molecular helical structure and the spin filtering effect. It was also established that the effect does not depend on the substrate used for making monolayer. Our phenomenological model shows that the spin filtering effect is due to the large spin orbit interaction of electrons during the translation through molecules having a helical potential. Exciting results on light controlled spin filtering effect and future research plan would be described in details.