Janus zigzag graphene nanoribbons for spin caloritronics

Abstract

Recently, a class of zigzag graphene nanoribbons (ZGNRs) with asymmetric and topological boundary conditions – known as Janus ZGNRs – has been experimentally realized (Song et al., 2025). In this work, we systematically investigate the electronic, magnetic, and spin-dependent thermoelectric properties of Janus ZGNRs with various widths and defect parameters using density functional theory combined with coherent transport formalism. The results reveal robust spin polarization, tunable band gaps, and spin-semiconducting behavior characterized by localized conduction and valence states. Remarkably, these features give rise to a giant spin Seebeck coefficient of up to 1490 μVK−1, exhibiting slight variation with changes in chemical potential. When a thermal gradient is applied across the nanoribbons, distinct spin-dependent thermal currents and tunable threshold temperatures emerge. Overall, the persistent spin-semiconducting nature of Janus ZGNRs, together with their structural asymmetry and topological edge configuration, ensures stable thermoelectric performance across different defect parameters and ribbon widths, making them promising candidates for graphene-based spintronic and spin-caloritronic devices.