Fundamental Properties of Superconductors and Mesoscopic Devices

超导体和介观器件的基本特性

• 批准号: 9701487
• 负责人: Michael Tinkham
• 金额: $ 54.3万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-07-01 至 2000-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9701487&HistoricalAwards=false
• 关键词: Fundamental; Properties; Superconductors; Mesoscopic; Devices

w:\awards\awards96\num.doc 9701487 Tinkham Experimental and theoretical work will be performed to elucidate the physical properties of superconducting and normal-metal devices fabricated on micron and nanometer length scales. In such mesoscopic structures, the Coulomb charging energy of a single electron exceeds thermal energies below 1K, allowing one to control the number of electrons one-by-one on the island in a single-electron transistor (SET). If the island is superconducting, the PI's previous work has shown that the pairing energy leads to even-odd electron number effects. One ongoing project will utilize this even-odd effect as the basis for developing a microwave detector device of unprecedented sensitivity, in which each individual microwave photon absorbed in enabling the photon-assisted tunneling of a single electron will trigger a microsecond long current pulse containing hundreds of electrons. The SET electrometers coupled to wide-band cryogenic amplifiers developed for this experiment will also make possible new types of experiments monitoring the motion of single electronic charges with microsecond time resolution. If the mesoscopic island is as small as 5nm, the PI's previous work has shown that individual electronic energy levels can be resolved, and that a spectroscopic even-odd effect exists even in the normal state because of the two-fold spin degeneracy. Such measurements will be extended to new types of mesoscopic systems such as chemically prepared metallic nanospheres of controlled size (which should allow more systematic probing of energy level statistics than is possible with random sized grains), carbon nanotubes, and possibly even individual large organic molecules. Another experiment in preparation seeks to observe the change in the spectrum of a superconducting nanograin when it is doped with 0,1,2 or more magnetic impurities, to compare with theoretical predictions. %%% There is a practical need to understand better the new basic physics which will govern attempts to devise ever more compact computers and memories. With this general motivation, the research which will be performed under this grant will focus on various forms of the single-electron transistor, or SET. An SET device consists of a small conducting island coupled to electrical leads by ultramall tunnel junctions and capacitively coupled to a gate electrode which controls the number of electrons on the island. Such SET devices can easily detect a single excess electron charge, in principle making possible an ultracompact memory element in which the binary "zero" and "one" are represented by the presence or absence of a single extra electron. Development of a technology from this concept is complicated by the sensitivity of the devices to background charge noise and the difficulty of reliable fabrication of such small devices. The proposed research may lead to progress in overcoming these difficulties. A possible approach which will be explored involves joining the fabrication technology of physics, for making connections, with the molecular engineering of organic chemistry, to make small charge storage elements. At such small length scales, classical physics must be replaced by quantum physics, in which the wave properties of electrons become important in understanding the electrical properties of the device. The research to be performed will probe the relation between the discrete set of quantum energy levels in a small conducing grain with the charging energies of classical electrostatics. Special attention will be paid to phenomena which arise from the pairing energy of electrons if the grain is superconducting, and to the coupling of the electron spins with d eliberately introduced magnetic impurity atoms. ***

W：\ Awards \ Awards96 \ num.Doc 9701487 Tinkham实验和理论工作，以阐明在微米和纳米长度尺度上制造的超导和正常金属设备的物理特性。在这样的介观结构中，单个电子的库仑充电能超过1K以下的热能，使一个电子能够以单电子晶体管（SET）的形式控制岛上的电子数量。 如果该岛是超导的，那么PI的先前工作表明，配对能量会导致偶数EDD电子数效应。 一个正在进行的项目将利用这种均匀的效果作为开发前所未有的灵敏度的微波检测器设备的基础，其中每个微波的光子吸收在使单个电子的光子辅助隧道中吸收的每个微波光子将触发一个微秒的长电流脉冲，其中包含数百个电子。 为该实验开发的宽波段低温放大器耦合的设置电测器还将使新型实验可能通过微秒时间分辨率监测单个电子电荷的运动。 如果介观岛小至5nm，则PI先前的工作表明可以解析单个电子能级，并且由于旋转的旋转二元性的两倍，光谱均匀的均匀效应即使在正常状态下也存在。 此类测量将扩展到新型的介观系统，例如具有控制大小的化学准备金属纳米球（这应该允许对能量水平统计的系统探测比随机大小的晶粒，碳纳米管的可能性更多），碳纳米管，甚至可能是单个大型有机分子。 制备的另一项实验试图观察超导纳米晶的光谱的变化，当它与0,1,2或更多的磁性杂质掺杂时，与理论预测进行了比较。 %%％的实际需求可以更好地理解新的基本物理学，这些物理学将控制尝试更多紧凑的计算机和记忆的尝试。 借助这种一般的动机，将根据该赠款进行的研究将重点放在各种形式的单电子晶体管或设置上。 设备设备由一个小型导电岛组成，该岛通过超大型隧道连接连接到电引线，并电容与控制岛上电子数量的栅极电极耦合。这样的设备可以轻松地检测到单个过量的电子电荷，从原则上讲，可以使二进制“零”和“一个”的超跨记忆元素以存在或不存在单个额外电子表示表示。 从这个概念开发技术的发展使设备对背景电荷噪声的敏感性以及可靠制造此类小型设备的难度。 拟议的研究可能导致克服这些困难的进展。将探索的一种可能的方法涉及将物理的制造技术与有机化学的分子工程建立连接，以制造少量电荷存储元件。在如此小的长度尺度下，必须用量子物理学代替经典物理，其中电子的波性能对于理解设备的电气性能很重要。 要进行的研究将探究小诱导谷物中离散的量子能级与经典静电的充电能量之间的关系。如果谷物是超导的，以及电子旋转与d具有d的磁性磁性杂质原子的偶联，则将特别注意这一现象，这些现象是由电子的配对能以及电子旋转的偶联而引起的。 ***