Spin current pumped by a rotating magnetic field in zigzag graphene nanoribbons.

Abstract

We study electron spin resonance in zigzag graphene nanoribbons by applying a rotating magnetic field on the system without any bias. By using the nonequilibrium Green's function technique, the spin-resolved pumped current is explicitly derived in a rotating reference frame. The pumped spin current density increases with the system size and the intensity of the transverse rotating magnetic field. For graphene nanoribbons with an even number of zigzag chains, there is a nonzero pumped charge current in addition to the pumped spin current owing to the broken spatial inversion symmetry of the system, but its magnitude is much smaller than the spin current. The short-ranged static disorder from either impurities or defects in the ribbon can depress the spin current greatly due to the localization effect, whereas the long-ranged disorder from charge impurities can avoid inter-valley scattering so that the spin current can survive in the strong disorder for the single-energy mode.

AI evidence extraction

Main findings

Using a nonequilibrium Green's function approach in a rotating reference frame, the authors derive spin-resolved pumped current in zigzag graphene nanoribbons under a transverse rotating magnetic field without applied bias. Pumped spin current density increases with system size and with the intensity of the transverse rotating magnetic field. For ribbons with an even number of zigzag chains, a nonzero pumped charge current is also predicted due to broken spatial inversion symmetry, but it is much smaller than the spin current; short-ranged static disorder can greatly depress the spin current, while long-ranged charge-impurity disorder can allow the spin current to survive in strong disorder for a single-energy mode.

Outcomes measured

• spin-resolved pumped current
• pumped spin current density
• pumped charge current
• effects of static disorder (impurities/defects) on spin current
• effects of long-ranged charge-impurity disorder on spin current

Limitations

• Appears to be a theoretical/modeling study (nonequilibrium Green's function) rather than experimental or epidemiological evidence.
• No quantitative exposure parameters (e.g., field strength, frequency) are provided in the abstract.
• No biological/health endpoints are assessed; outcomes are electronic transport properties in graphene nanoribbons.

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "rotating magnetic field",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "spin-resolved pumped current",
        "pumped spin current density",
        "pumped charge current",
        "effects of static disorder (impurities/defects) on spin current",
        "effects of long-ranged charge-impurity disorder on spin current"
    ],
    "main_findings": "Using a nonequilibrium Green's function approach in a rotating reference frame, the authors derive spin-resolved pumped current in zigzag graphene nanoribbons under a transverse rotating magnetic field without applied bias. Pumped spin current density increases with system size and with the intensity of the transverse rotating magnetic field. For ribbons with an even number of zigzag chains, a nonzero pumped charge current is also predicted due to broken spatial inversion symmetry, but it is much smaller than the spin current; short-ranged static disorder can greatly depress the spin current, while long-ranged charge-impurity disorder can allow the spin current to survive in strong disorder for a single-energy mode.",
    "effect_direction": "unclear",
    "limitations": [
        "Appears to be a theoretical/modeling study (nonequilibrium Green's function) rather than experimental or epidemiological evidence.",
        "No quantitative exposure parameters (e.g., field strength, frequency) are provided in the abstract.",
        "No biological/health endpoints are assessed; outcomes are electronic transport properties in graphene nanoribbons."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "zigzag graphene nanoribbons",
        "electron spin resonance",
        "rotating magnetic field",
        "nonequilibrium Green's function",
        "spin pumping",
        "pumped spin current",
        "pumped charge current",
        "disorder",
        "impurities",
        "defects",
        "localization",
        "inter-valley scattering"
    ],
    "suggested_hubs": []
}

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