Renewal: Fundamental Physics of Polariton Condensates

更新：极化子凝聚体的基础物理

• 批准号: 2306977
• 负责人: David Snoke
• 金额: $ 75.83万
• 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: 2024
• 资助国家: 美国
• 起止时间: 2024-04-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2306977&HistoricalAwards=false
• 关键词: Renewal; Fundamental; Physics; Polariton; Condensates

Nontechnical decription:This project, funded jointly by the Condensed Matter Physics and Atomic, Molecular and Optical Physics - Experiment programs, supports fundamental physics studies in a new class of superfluids. Superfluidity is an intrinsically quantum phenomenon in which below a certain temperature, many particles spontaneously join together to act as a wave. There are just a few physical systems that are known to act this way. The oldest is superfluid liquid helium, which flows with zero viscosity. Superconducting metals are another example, in which electrons act as a wave, and flow with zero resistance, and ultracold atoms in ultrahigh vacuum, stabilized by laser beams and magnetic field are another. In the past decade, another class of superfluid has received widespread attention, namely “heavy photons” known as “polaritons,” in which photons can flow like a liquid. This project supports basic research studies of these polariton superfluids, made possible by using semiconductor structures, fabricated as part of this project, that are the best in the world in terms of smoothness and lack of impurities. This project can have broad impact in increasing our understanding of universal properties of superfluids, and in making possible new types of optical communications devices. The PI of the project will also continue to collaborate with the Carnegie Science Center in Pittsburgh to educate the public on general quantum mechanics and optics topics.Technical description: This project supports the continuing work of PI Snoke on fundamental properties of exciton-polaritons in GaAs-AlGaAs microcavities. The structures are designed by the Snoke group and then fabricated using molecular-beam epitaxy by two labs, the group of Loren Pfeiffer at Princeton and the group of Zbig Wasilewski at the University of Waterloo. One goal of the project is to advance the quality of these microcavity structures, in particular to make large area structures with a high degree of flatness and very little leakage of light out of the structures, which will allow the possibility of optical circuits on a chip with propagation lengths of hundreds of microns. The Snoke group will use advanced optical methods including picosecond time-resolved spectroscopy, imaging, and interferometry to study polariton superfluids in these structures. In the past year, two breakthrough results have been obtained, and an immediate goal will be to perform followup experiments to fully understand these effects. One of these is the demonstration of a true persistent current of a polariton superfluid in a ring. While indirect evidence for persistent current has been seen in other systems, the microcavity polariton system allows direct, in situ measurement of the phase of the superfluid while it is circulating. The other new result is a highly accurate measurement of the superfluid fraction while the system is in thermal equilibrium. A universal power law has been observed which was not theoretically predicted nor observed in other experimental systems. Ongoing collaboration with many-body theorists will seek to create an analytical model for this power law. In the longer term, this project will seek to make networks of coupled polariton superfluids, which can be used both for ultrafast (~10 ps) optical switching methods as well as novel methods of analog optical computing to solve mathematical problems that are hard for traditional computers.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.

非技术描述：该项目由凝聚态物理和原子、分子和光学物理实验项目联合资助，支持一种新型超流体的基础物理研究。超流体本质上是一种量子现象，在一定温度下，许多粒子自发地结合在一起，形成波。只有少数物理系统是这样运作的。最古老的是超流体液氦，它以零粘度流动。超导金属是另一个例子，其中电子作为波，以零电阻流动，以及超高真空中的超冷原子，由激光束和磁场稳定。在过去的十年里，另一类超流体受到了广泛的关注，即“重光子”，即“极化子”，光子可以像液体一样流动。该项目支持对这些极化子超流体的基础研究，通过使用半导体结构使之成为可能，半导体结构是该项目的一部分，在平滑度和缺乏杂质方面是世界上最好的。这个项目可以在增加我们对超流体的普遍性质的理解方面产生广泛的影响，并使新型光通信设备成为可能。该项目的PI还将继续与匹兹堡的卡内基科学中心合作，向公众普及量子力学和光学方面的知识。技术描述：该项目支持PI Snoke继续研究GaAs-AlGaAs微腔中激子极化子的基本性质。这些结构由Snoke小组设计，然后由普林斯顿大学的Loren Pfeiffer小组和滑铁卢大学的Zbig Wasilewski小组两个实验室使用分子束外延技术制造。该项目的目标之一是提高这些微腔结构的质量，特别是制造具有高度平直度的大面积结构，并且很少有光从结构中泄漏出来，这将使在芯片上传播长度为数百微米的光学电路成为可能。Snoke小组将使用先进的光学方法，包括皮秒时间分辨光谱、成像和干涉测量来研究这些结构中的极化子超流体。在过去的一年里，已经取得了两个突破性的结果，而近期的目标将是进行后续实验，以充分了解这些效应。其中之一是证明了环中极化子超流体的真正持续电流。虽然在其他系统中已经看到了持续电流的间接证据，但微腔极化子系统允许在超流体循环时直接原位测量其相位。另一个新结果是在系统处于热平衡状态时对超流体分数的高精度测量。一个普遍的幂律已经被观察到，这在理论上没有被预测，也没有在其他实验系统中被观察到。与多体理论学家正在进行的合作将寻求为这一幂律创建一个分析模型。从长远来看，该项目将寻求建立耦合极化子超流体网络，它既可以用于超快（~10 ps）光交换方法，也可以用于模拟光计算的新方法，以解决传统计算机难以解决的数学问题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。