Artificial Atoms

人造原子

• 批准号: 0102153
• 负责人: Marc Kastner
• 金额: $ 30万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-01 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0102153&HistoricalAwards=false
• 关键词: Artificial; Atoms

Experiments are proposed to explore the physics of electrons confined to a small region of space and coupled to nearby metallic leads. The particular system to be studied is the single-electron transistor (SET). Experiments carried out in the past few years have revealed the effects of strong coupling between the confined electron droplet and the leads in an SET. In particular, they have demonstrated that the Anderson Hamiltonian, together with scaling and renormalization theories, provides a quantitative description of the equilibrium (zero-bias) conductance as a function of temperature and gate voltage. Specifically, the ground state of the coupled system is a Kondo singlet. The publication of these results has stimulated a number of theoretical predictions, and one goal of the proposed research is to test these predictions. The differential conductance as a function of bias will be studied. In addition, the effects of multiple levels on the Kondo effect will be examined. In a magnetic field the peak in differential conductance associated with the Kondo singlet splits in two. Predictions have been made of the splitting of these peaks and the evolution of their line shape with magnetic field will be tested. A new measurement facility has been constructed which will allow the measurement of the Kondo effect to be extended to lower temperature. The system is equipped with a 16T magnet and rotation stage, so that the field can be in the plane or perpendicular to the plane of the droplet of electrons. This will allow the measurement of the temperature dependence of the Kondo peak in differential conductance precisely. A completely different phenomenon, recently discovered in SETs, is Fano interference. For small SETs the single-electron line shapes are asymmetric with the characteristic shape predicted by the Fano theory. The latter requires a continuous transmission channel that interferes with a resonant one. Experiments are planned to clarify the nature of this interference. In particular, while the resonant channel appears to arise from single electron addition, the origin of the continuous channel is a mystery. Measurement of the temperature and magnetic field dependence of the line shapes may clarify the microscopic physics. This research will be done with students who will thereby receive training in a cutting edge area of nanoscience and technology. %%%The most dramatic phenomenon of the last half of the twentieth century is the technological revolution, driven by the decrease in cost and increase in efficiency of semiconductor technology. We often describe this by "Moore's Law", the exponential increase in the number of transistors on a silicon chip. The latter number has been increasing by a factor two every eighteen months for over forty years. This explosion was made possible by discoveries in fundamental semiconductor physics. However, in order to sustain it, scientists and engineers needed new technologies for making smaller and smaller structures, so that it is now possible to make semiconductor structures that are only nanometers in size. Whereas electrons in conventional transistors behave like classical particles, electrons confined to small dimensions can only be described by quantum mechanics. Thus, discoveries in physics led to new technology, which now make it possible for us to study new physics. This research will explore the physics of electrons confined to nanometer dimensions. The structure focused on is called a single electron transistor (SET). A transistor is a switch that turns on when electrons are added to it and turns off when they are removed. The conventional transistor of today, in a cellular telephone or personal computer, for example, requires about 1000 electrons to turn on. The SET turns on and off again every time a single electron transistor is added to it. The goal of this research is to understand how the electron is distributed between the trap and the electrodes of the transistor and how this distribution depends on the properties of the SET, the temperature and an applied magnetic field. The physics is expected to be similar for a wide variety of nano-electronic structures and so will be of broad application to nanoscience and nanotechnology. Graduate and undergraduate students will participate in this research. They will receive training in one of the forefront areas of nanoscience and nanotechnology that will prepare them for employment in academe, industry and government institutions. ***

有人提议进行实验，以探索受限于小空间区域并耦合到附近金属导线的电子的物理学。要研究的特殊系统是单电子晶体管(SET)。过去几年进行的实验揭示了受限电子液滴与一组导线之间的强耦合效应。特别是，他们证明了Anderson哈密顿量与标度和重整化理论一起，提供了平衡(零偏压)电导作为温度和门电压的函数的定量描述。具体地说，耦合系统的基态是近藤单态。这些结果的发表刺激了许多理论预测，拟议研究的一个目标是测试这些预测。我们将研究作为偏置的函数的微分电导。此外，还将考察多个水平对近藤效应的影响。在磁场中，与近藤单线态有关的微分电导的峰值分裂成两半。对这些峰的分裂进行了预测，并将检验它们的线形随磁场的演变。已经建造了一个新的测量设施，可以将近藤效应的测量扩展到较低的温度。该系统配备了16T磁铁和旋转台，使磁场可以在电子液滴的平面内或垂直于该平面。这将允许精确地测量差分电导中近藤峰的温度依赖关系。最近在SET中发现的一个完全不同的现象是Fano干扰。对于小集合，单电子线形是不对称的，符合Fano理论所预测的特征形状。后者需要一个连续的传输通道，该通道会干扰谐振通道。计划进行实验，以澄清这种干扰的性质。特别是，虽然共振通道似乎是由单电子加成而来，但连续通道的起源是一个谜。测量线条形状与温度和磁场的关系可以阐明微观物理。这项研究将与接受纳米科学和技术尖端领域培训的学生一起进行。20世纪后半叶最引人注目的现象是技术革命，其驱动因素是半导体技术成本的降低和效率的提高。我们经常用“摩尔定律”来描述这一现象，摩尔定律指的是硅芯片上晶体管数量的指数增长。40多年来，这一数字每18个月增加一倍。这种爆炸是由于基础半导体物理的发现而成为可能的。然而，为了维持它，科学家和工程师需要制造越来越小的结构的新技术，这样现在才有可能制造只有纳米大小的半导体结构。虽然传统晶体管中的电子行为类似于经典粒子，但受限于小维度的电子只能用量子力学来描述。因此，物理学的发现导致了新的技术，这使得我们现在有可能研究新的物理学。这项研究将探索纳米尺度下的电子物理学。所关注的结构称为单电子晶体管(SET)。晶体管是一种开关，当电子被添加到晶体管上时，它就会打开，当电子被移除时，它就会关闭。例如，今天的传统晶体管，在移动电话或个人电脑中，需要大约1000个电子才能开启。每次增加一个单电子晶体管时，电视机就会再次开启和关闭。这项研究的目的是了解电子是如何在晶体管的陷阱和电极之间分布的，以及这种分布如何依赖于器件的性质、温度和外加磁场。预计各种纳米电子结构的物理学将是相似的，因此将在纳米科学和纳米技术中得到广泛应用。研究生和本科生将参与这项研究。他们将接受纳米科学和纳米技术前沿领域之一的培训，为他们在学术界、工业界和政府机构就业做好准备。***