Fundamental Studies of Bose-Einstein Condensates of Polaritons

非技术摘要：本项目研究低温下半导体结构中光学态的量子力学基本效应。这个项目特别关注玻色-爱因斯坦凝聚(BEC)的过程，在这个过程中，许多粒子进入一个单一的量子态。这里所研究的BEC是由“极化子”组成的，它可以被看作是具有特殊性质的光子；例如，它们像原子一样具有质量并且相互排斥。在低温下，人们对原子气体中的BEC进行了广泛的研究；这项关于极化子BEC的项目为原子BEC的研究提供了新的视角，是对这一研究的补充。特别是，这个项目中研究的系统像激光一样发出相干光，可以用先进的光学方法进行研究。该项目的首席研究员(PI)还将与匹兹堡的卡内基科学中心密切合作，向公众介绍量子力学的基本概念。技术摘要：这个项目建立在以前关于玻色-爱因斯坦极化子凝聚的成功工作的基础上，追求三个主要目标：1)匹兹堡大学的实验旨在建立平衡条件下BEC的相图，包括准确地确定凝聚分数作为密度和温度的函数；2)匹兹堡大学的实验将研究BEC的开始，从“猝灭”(高度非平衡态)一直到完全平衡，在准一维导线中；以及3)匹兹堡大学的实验将研究圆环中凝聚态的宏观相干态，包括自旋织构和量子化角动量状态。上述实验涉及匹兹堡斯诺克实验室提供的超快时间分辨光学光谱、成像和干涉测量方法。对于每一次推力，在匹兹堡大学设计的样品都是在普林斯顿大学和滑铁卢大学通过分子束外延生长出来的，然后运往匹兹堡，在匹兹堡大学的无尘室进行最后处理。这一过程包括蚀刻结构，以制造用于控制极化子凝聚体流动的一维导线。这些实验的结果是与来自包括芝加哥大学、斯特拉斯克莱德大学、伍尔弗汉普顿大学和匹兹堡大学在内的其他大学的理论家团队合作研究的，以解决基本问题，例如相互作用对凝析油耗尽的影响，不平衡凝聚体的阻尼理论，以及凝聚体的拓扑非平凡状态。该材料研究部(DMR)拨款支持研究，以了解平衡和非平衡条件下BEC的相图，资金来自DMR和原子的凝聚态物理(CMP)计划，分子和光学物理-实验(AMO-E)计划在数学和物理科学(MPS)局长的物理部(PHY)。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Abstract:This project studies fundamental effects of quantum mechanics of optical states in semiconductor structures at low temperature. In particular, this project focuses on the process of Bose-Einstein condensation (BEC), in which many particles enter a single quantum state. The BEC studied here is comprised of “polaritons,” which can be viewed as photons with special properties; for example, they have mass and repel each other, like atoms. BEC has been studied extensively in gases of atoms at low temperature; this project on BEC of polaritons complements the study of BEC of atoms by providing new ways of looking at the system. In particular, the system under study in this project emits coherent light like a laser, which can be studied using advanced optical methods. The principle investigator (PI) of the project will also work closely with the Carnegie Science Center in Pittsburgh to present basic concepts of quantum mechanics to the public. Technical Abstract:This project builds on previous successful work on Bose-Einstein condensation of polaritons by pursuing three main goals: 1) Experiments at the University of Pittsburgh will aim at establishing the phase diagram of BEC under equilibrium conditions, including accurate determination of the condensate fraction as a function of density and temperature; 2) experiments at the University of Pittsburgh will study the onset of BEC from a “quench” (a highly nonequilibrium state) all the way to full equilibrium, in quasi-one-dimensional wires; and 3) experiments at the University of Pittsburgh will study macroscopic coherent states of a condensate in a circular ring, including spin texture and quantized angular momentum states. The above experiments involve ultrafast time-resolved optical spectroscopy, imaging, and interferometry methods available in the Snoke laboratories in Pittsburgh. For each of these thrusts, samples designed at the University of Pittsburgh are grown by molecular beam epitaxy at Princeton University and at the University of Waterloo, then delivered to Pittsburgh for final processing in the clean room at the University of Pittsburgh. This processing includes etching the structures to make one-dimensional wires for controlling the flow of the polariton condensate. The results of these experiments are studied in collaboration with a team of theorists from other universities including the University of Chicago, the University of Strathclyde, the University of Wolverhampton, and the University of Pittsburgh to address fundamental questions, such as the effect of interactions on depletion of the condensate, the theory of damping of a condensate out of equilibrium, and topologically nontrivial states of a condensate.This Division of Materials Research (DMR) grant supports research to understand the phase diagram of BEC under equilibrium and non-equilibrium conditions with funding from the Condensed Matter Physics (CMP) Program in DMR and the Atomic, Molecular and Optical Physics - Experiment (AMO-E) program in the Division of Physics (PHY) both of the Mathematical and Physical Sciences (MPS) Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.