Chiral Induced Spin Selectivity (CISS): Unraveling the Theoretical Underpinnings and Implications in Molecular Electronics and Spintronics

Chiral-induced Spin Selectivity or CISS has been a term used to encompass a variety of compelling experiments on molecules with either point or helical chirality (or a combination), amino acids, B-DNA, oligopeptides, Photosystem I, Alpha helices, helicene among many others that appear to be strikingly efficient in polarizing electron spin. Spin Polarization is measured in three emblematic configurations: i) Electron beam through a gas phase of point chiral molecules, ii) Photo-electrons through self-assembled monolayers, iii) Two terminal transport measurements producing spin accumulation on a metallic terminal/spin-dependent changes in the resistance in a molecular circuit. We will review the theory attempting to describe the spin-polarization and provide evidence for CISS as a stand-alone effect of chiral molecules whose spin active ingredient is the spin-orbit interaction (due to a source of inversion asymmetry such as chirality) and for two terminal setups, requires a source of time-reversal symmetry-breaking. Further, tunneling in two terminal setups exponentially enhances spin polarization to the experiments' orders.