{
  "id": "1212.5474",
  "version": "v1",
  "published": "2012-12-21T15:05:06.000Z",
  "updated": "2012-12-21T15:05:06.000Z",
  "title": "Shot noise of spin current and spin transfer torque",
  "authors": [
    "Yunjin Yu",
    "Hongxin Zhan",
    "Langhui Wan",
    "Bin Wang",
    "Yadong Wei",
    "Qingfeng Sun",
    "Jian Wang"
  ],
  "comment": "15pages, 6figures",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.mtrl-sci"
  ],
  "abstract": "We report the theoretical investigation of noise spectrum of spin current and spin transfer torque for non-colinear spin polarized transport in a spin-valve device which consists of normal scattering region connected by two ferromagnetic electrodes. Our theory was developed using non-equilibrium Green's function method and general non-linear $S^\\sigma-V$ and $S^\\tau-V$ relations were derived as a function of angle $\\theta$ between magnetization of two leads. We have applied our theory to a quantum dot system with a resonant level coupled with two ferromagnetic electrodes. It was found that for the MNM system, the auto-correlation of spin current is enough to characterize the fluctuation of spin current. For a system with three ferromagnetic layers, however, both auto-correlation and cross-correlation of spin current are needed to characterize the noise spectrum of spin current. Furthermore, the spin transfer torque and the torque noise were studied for the MNM system. For a quantum dot with a resonant level, the derivative of spin torque with respect to bias voltage is proportional to $\\sin\\theta$ when the system is far away from the resonance. When the system is near the resonance, the spin transfer torque becomes non-sinusoidal function of $\\theta$. The derivative of noise spectrum of spin transfer torque with respect to the bias voltage $N_\\tau$ behaves differently when the system is near or far away from the resonance. Specifically, the differential shot noise of spin transfer torque $N_\\tau$ is a concave function of $\\theta$ near the resonance while it becomes convex function of $\\theta$ far away from resonance. For certain bias voltages, the period $N_\\tau(\\theta)$ becomes $\\pi$ instead of $2\\pi$. For small $\\theta$, it was found that the differential shot noise of spin transfer torque is very sensitive to the bias voltage and the other system parameters.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-12-21T15:05:06.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "spin transfer torque",
      "spin current",
      "bias voltage",
      "far away",
      "noise spectrum"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0957-4484/24/15/155202",
      "journal": "Nanotechnology",
      "year": 2013,
      "month": "Apr",
      "volume": 24,
      "number": 15,
      "pages": 155202
    },
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2013Nanot..24o5202Y"
    }
  }
}