Spin Filtering through Single-Wall Carbon Nanotubes Functionalized with Single-Stranded DNA

High spin polarization materials or spin filters are key components in spintronics, a niche subfield of electronics where carrier spins play a functional role. Carrier transmission through these materials is spin selective, that is, these materials are able to discriminate between up and down spins. Common spin filters include transition metal ferromagnets and their alloys, with typical spin selectivity (or, polarization) of approximate to 50% or less. Here carrier transport is considered in an archetypical one-dimensional molecular hybrid in which a single wall carbon nanotube (SWCNT) is wrapped around by single stranded deoxyribonucleic acid (ssDNA). By magnetoresistance measurements it is shown that this system can act as a spin filter with maximum spin polarization approaching approximate to 74% at low temperatures, significantly larger than transition metals under comparable conditions. Inversion asymmetric helicoidal potential of the charged ssDNA backbone induces a Rashba spin-orbit interaction in the SWCNT channel and polarizes carrier spins. The results are consistent with recent theoretical work that predicted spin dependent conductance in ssDNA-SWCNT hybrid. Ability to generate highly spin polarized carriers using molecular functionalization can lead to magnet-less and contact-less spintronic devices in the future. This can eliminate the conductivity mismatch problem and open new directions for research in organic spintronics.