Spin-seebeck effect and thermal colossal magnetoresistance in the narrowest zigzaggraphene nanoribbons.

Device miniaturization and low-energy dissipation are two urgent needs in future spintronics devices. The narrowest zigzag graphene nanoribbons (ZGNRs), which are composed only by two coupled carbon-atom chains connected with carbon tetragons, are promising candidates to meet well the above both requirements. Using the first-principles calculations combined with nonequilibrium Green's function approach, thermal spin-dependent transport through this kind of the narrowest ZGNRs is investigated and uncovers several exotic thermal spin-resolved transport properties: (i) when an external magnetic field is applied, the ZGNRs are transited from intrinsic semiconducting to metallic state and thermal colossal magnetoresistance effect (TCMR) occurs with the order of magnitudes up to 104at room temperature; (ii) the thermal spin-dependent currents display a thermal negative differential resistance effect (NDRE), and a well-defined spin-Seebeck effect (SSE) together with a pure thermal spin current occurs and (iii), under suitable device temperature settings, a nearly perfect spin-filtering effect (SFE) occurs in these narrowest ZGNRs. Theoretical results not only uncover the narrowest nanoribbon structures to realize the SSE and other inspiring thermal spin transport features, but also push carbon-based material candidates towards thermoelectric conversion device applications.