Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Department of Physics, Harvard University, Cambridge, MA 02138, USA. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
Science. 2015 Mar 6;347(6226):1129-32. doi: 10.1126/science.aaa4298. Epub 2015 Jan 29.
Thermally induced electrical currents, known as Johnson noise, cause fluctuating electric and magnetic fields in proximity to a conductor. These fluctuations are intrinsically related to the conductivity of the metal. We use single-spin qubits associated with nitrogen-vacancy centers in diamond to probe Johnson noise in the vicinity of conductive silver films. Measurements of polycrystalline silver films over a range of distances (20 to 200 nanometers) and temperatures (10 to 300 kelvin) are consistent with the classically expected behavior of the magnetic fluctuations. However, we find that Johnson noise is markedly suppressed next to single-crystal films, indicative of a substantial deviation from Ohm's law at length scales below the electron mean free path. Our results are consistent with a generalized model that accounts for the ballistic motion of electrons in the metal, indicating that under the appropriate conditions, nearby electrodes may be used for controlling nanoscale optoelectronic, atomic, and solid-state quantum systems.
热致电流，即约翰逊噪声，会在导体附近产生波动的电场和磁场。这些波动与金属的导电性密切相关。我们利用与钻石中的氮空位中心相关联的单自旋量子位来探测附近导电银膜中的约翰逊噪声。在一系列距离（20 到 200 纳米）和温度（10 到 300 开尔文）下对多晶银膜的测量结果与磁波动的经典预期行为一致。然而，我们发现，在单晶膜旁边，约翰逊噪声明显受到抑制，这表明在电子平均自由程以下的长度尺度上，欧姆定律发生了实质性偏离。我们的结果与一个广义模型一致，该模型解释了金属中电子的弹道运动，这表明在适当的条件下，附近的电极可用于控制纳米级光电、原子和固态量子系统。
