Spontaneous Pattern Formation and Spontaneous Coherence of Excitons in Coupled Quantum Wells

耦合量子阱中激子的自发图案形成和自发相干性

• 批准号: 0404912
• 负责人: David Snoke
• 金额: $ 41.4万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0404912&HistoricalAwards=false
• 关键词: Spontaneous; Pattern; Formation; Coherence; Excitons

This condensed matter physics project focuses on two novel effects in the optics of semiconductor quantum well structures. The first is the appearance of sharply-defined luminescence rings at the interface of a two-dimensional electron gas and a two-dimensional hole gas. This project will explore the role of Coulomb pressure, the nature of wavelike propagation in the hole gas, and the effects of externally applied stress and magnetic field on this phenomenon. The project will also aim at understanding the appearance of periodic structures in the rings. which have been reported by another experimental group. The second topic is the long-predicted phenomenon of spontaneous coherence of excitons at low temperature. This project will develop new designs of the quantum well structures to maximize the mobility and lifetime of the excitons. A major aim is to understand the role of disorder in these systems. This project will use a method of confining the excitons in an in-plane harmonic potential, developed in earlier NSF-supported work, to make possible a Bose-Einstein condensate of excitons in two dimensions. Students and post-doctoral associates will receive training in cutting edge research that will prepare them for careers in academe, industry, and government.In semiconductor structures with layers that have a thickness of just a few nanometers, electrons can be confined to two-dimensional motion. This creates a negatively-charged "two-dimensional electron gas." In the same way, a positively-charged two-dimensional gas can be created, comprised of "holes" (missing electrons in one of the electron bands.) Earlier work has shown it is possible to create both of these types of gases in a single two-dimensional plane, and when this happens, a bright light emission at the interface between the two gases is observed. This project will aim at greater understanding of this recently-discovered effect, using cryogenics, magnetic field, and stress to probe the system. In addition, electrons and holes in this type of semiconductor nanostructure are predicted to spontaneously acquire coherence similar to that of a laser or a superconductor. Some research groups have already reported this to occur, but their claims depend strongly on understanding the role of disorder in the samples. This project will aim to create this novel state of matter in a controlled way, using new designs of semiconductor quantum well structures with low disorder and new experimental methods for confining the electrons and holes to a small region in the two-dimensional plane. If this state is verified, it would be as significant as a new type of superconductor. Students and post-doctoral associates will receive training in cutting edge research that will prepare them for careers in academe, industry, and government.

这个凝聚态物理学项目集中在半导体量子阱结构光学中的两个新效应。首先是在二维电子气和二维空穴气的界面处出现清晰的发光环。本计画将探讨库仑压力的作用、孔隙气体中波动传播的本质，以及外加应力与磁场对这种现象的影响。该项目还旨在了解环中周期性结构的外观。这是另一个实验小组报告的。第二个主题是长期预测的激子在低温下的自发相干现象。该项目将开发量子阱结构的新设计，以最大限度地提高激子的迁移率和寿命。 一个主要目的是了解这些系统中的无序的作用。该项目将使用一种将激子限制在平面内谐波势中的方法，该方法是在早期NSF支持的工作中开发的，以使二维激子的玻色-爱因斯坦凝聚成为可能。学生和博士后将接受前沿研究的培训，为他们在工业、工业和政府部门的职业生涯做好准备。在厚度仅为几纳米的半导体结构中，电子可以被限制在二维运动。这就产生了带负电荷的“二维电子气”。以同样的方式，可以产生一种带正电的二维气体，由“空穴”（其中一个电子带中缺少电子）组成。 早期的工作已经表明，在一个二维平面上同时产生这两种气体是可能的，当这种情况发生时，在两种气体之间的界面处观察到明亮的光发射。该项目旨在更好地了解这种最近发现的效应，使用低温，磁场和应力来探测系统。此外，在这种类型的半导体纳米结构中的电子和空穴被预测自发地获得类似于激光或超导体的相干性。一些研究小组已经报道了这种情况，但他们的说法在很大程度上取决于对样本中紊乱作用的理解。该项目旨在以可控的方式创造这种新的物质状态，使用具有低无序的半导体量子阱结构的新设计和将电子和空穴限制在二维平面中的一个小区域的新实验方法。如果这种状态得到验证，它将与一种新型超导体一样重要。学生和博士后将接受前沿研究的培训，为他们在工业，工业和政府的职业生涯做好准备。