Enhancing Spin Coherence in Metallic Single Walled Carbon Nanotubes Utilizing Chiral Perturbations

Quantum interference governs the transport behavior of low-dimensional conductors, where the phase coherence of scattered electrons gives rise to phenomena such as weak localization (WL) and weak anti-localization (WAL). Understanding how molecular environments influence these effects is crucial for advancing spin-dependent transport at the nanoscale. Here, we investigate the magneto-conductance of metallic single-walled carbon nanotube (m-SWNT) devices under conditions in which chiral molecules and chiral polymers interact with the nanotube surface. Pristine m-SWNTs display a WL-like feature, characterized by a narrow conductance dip around zero magnetic field, which is consistent with coherent backscattering in the absence of strong spin-orbit coupling. Following the adsorption of chiral molecules, the magneto-conductance evolves into a WAL profile, indicating the emergence of spin–orbit coupling (SOC) associated with the chiral overlayer. Moreover, extremely long coherence length is measured for spin transport in the chiral material. Utilizing a polymer that wraps the m-SWNT surface with a fixed helical pitch and in a single-handed fashion yields a stronger WAL response and higher effective SOC. These results demonstrate that molecular chirality can modulate quantum interference and spin–orbit interactions in carbon-based nanostructures, offering new pathways to control spin transport through molecular design.