Carbon-atom-chain-based spin filters

In this work, we theoretically investigate the spin transport properties of carbon atomic chain (CAC) junctions inserted between two silver leads. We focus on the effects of coupling strength, carbon atom parity, doping, and bias voltage. Density-functional theory and the non-equilibrium Green's function (DFT-NEGF) transport calculations have been employed to calculate the transmission spectra, electron distributions, and current–voltage characteristics. To further understand the underlying spin transport mechanisms, we develop a semiempirical tight-binding model integrated with NEGF theory and a mean-field Hubbard model. Our DFT-NEGF calculations indicate that the weak CAC-lead coupling, odd-numbered CAC as well as CAC doping with atoms such as oxygen, boron, or sulfur enhance the spin-filtering effect. In addition, the spin-filtering performance is also found to be affected by the bias voltage. These findings highlight the metal–lead–CAC systems as promising candidates for spintronic devices, with the ability to engineer their spin transport properties through precise control of their structural and magnetic configurations.