Dynamical Effects in Mesoscale Electronic Systems

本研究是对半导体微结构和金属/超导混合体系中动态介观输运现象的实验研究。统一的主题是三个元素之间的相互作用：量子相干、无序或混沌，以及依赖于时间的势的形式的动力学。所提出的实验还具有使用循环振荡势直流泵浦电荷的共同主题，扩展了最近关于绝热量子泵浦的工作，包括退相干、耗散和非绝热时间依赖的作用。除了形状可变形的量子点，还提出了两种新颖的泵浦装置：一种是工作在分数量子霍尔区的泵浦，允许泵浦分数带电的准粒子；另一种是混合金属-超导体，它利用交流约瑟夫森效应来产生边界条件的循环时间演化。这项研究将在哈佛大学的一个新实验室进行。该项目将资助一名研究生以及实验所需的材料和用品。参与这些项目的其他学生将得到独立奖学金的支持。这些学生将接受最先进的纳米电子技术培训，并将为在学术界、行业或政府的职业生涯做好准备。微电子的趋势有两个明确的方向：更小和更快。对电子设备中的量子力学效应的研究--特别是无序或混沌系统--被称为介观物理，在介观物理中，“介观”指的是介于原子(量子物理学被很好地理解)和受欧姆定律和其他熟悉的经典定律支配的大型经典电子学领域之间的中等大小。在过去的十年里，介观物理学取得了快速的发展，这主要是由于清洁半导体器件制造方面的进步。相比之下，在高速方面所做的工作很少，关于量子相干设备的大部分已知仅限于直流电。这项拟议的实验工作旨在研究由半导体和金属/超导混合器件制成的高频量子相干电子器件，当时间演化效应可以导致量子相干效应被破坏时，也可以导致新的效应，如由于器件有效形状的周期性、周期性变化而产生的电子泵浦。这些结果将影响我们对高速纳米电子学的理解和发展。该项目将支持一名研究生，并为该项目提供材料和用品。从事这些实验的其他学生将从NSF和其他来源获得外部资金。这些学生将接受最先进的纳米电子技术培训，并将为在学术界、行业或政府的职业生涯做好准备。

This research is an experimental study of dynamic mesoscopic transport phenomena in semiconductor microstructures and hybrid metals/superconductor systems. The unifying theme is the interplay between three elements: quantum coherence, disorder or chaos, and dynamics in the form of a time-dependent potential. The proposed experiments also have in common the theme of dc pumping of charge using cyclic oscillating potentials, extending recent work on adiabatic quantum pumping to include the role of decoherence, dissipation, and nonadiabatic time dependence. Besides shape-deformable quantum dots, two novel pumping devices are proposed: a pump that operates in the fractional quantum Hall regime, allowing a pumping of fractionally charged quasiparticles, and a hybrid metal-superconductor that uses the ac Josephson effect to produce a cycling time evolution of boundary conditions. This research will be carried out in a new laboratory at Harvard University. The project will support a graduate student as well as materials and supplies needed for the experiments. Other students on these projects will be supported by independent fellowships. The students will be trained in state-of-the-art nanoelectronics techniques and will be well prepared for careers in academe, industry or government. %%%Trends in microelectronics have two clear directions, smaller and faster. The study of quantum mechanical effects in electronic devices-particularly disorder or chaotic systems-is known as mesoscopic physics, where "meso" indicates intermediate in size between atoms (where quantum physics is well understood) and the realm of large, classical electronics, governed by Ohm's law and other familiar classical laws. Mesoscopic physics has seen rapid development in the last decade, predominantly as a result of advances in the fabrication of clean semiconductors devices. By comparison, little work has been done on the high-speed side, and most of what is known about quantum-coherent devices is restricted to dc. The proposed experimental work aims to investigate quantum coherent electronic devices fabricated from semiconductors and hybrid metal/superconductor devices, at high frequencies, when effects of time evolution can lead to the destruction of quantum coherence effects, but can also lead to new effects such as the pumping of electrons due to cyclic, periodic changes in the effective shape of the device. These results will impact our understanding and development of high-speed nanoelectronics. The project will support one graduate student as well as provide materials and supplies for the project. Other students working on these experiments will have outside funding from the NSF and other sources. The students will be trained in state-of-the-art nanoelectronics techniques and will be well prepared for careers in academe, industry or government.