Length-Dependent Electron Spin Polarization in Oligopeptides and DNA

The effect of spin polarization in conduction and in electric field-induced polarization was measured for double-stranded DNA oligonucleotides and oligopeptides of different lengths. These measurements were conducted using magnetic contact AFM, spin-dependent electrochemistry, spin-dependent polarization, and magnetoresistance studies. It was established that the spin-dependent conduction through chiral molecules depends on the voltage applied with a power of d, when d is larger than unity, and that there is a different voltage threshold for conducting each of the spin polarizations. In addition, there is no spin flipping during the conduction through the chiral system. The spin polarization depends linearly on the length, within the range of lengths studied, and it seems to scale like the optical activity. These results suggest the importance of the electric polarizability in the chiral-induced spin selectivity process. It was also shown that the preferred spin back scattering is suppressed, compared with the nonpreferred spin, probably as a result of the coupling between the electron's linear momentum and its spin as a result of the chiral potential.