CAREER: Correlated Excitons in Semiconducting Moire Superlattices

非技术文摘：基本粒子可分为费米子和玻色子，它们具有不同的集体行为。电子之间的相互作用，一种费米子，导致了现在众所周知的涌现特性。另一方面，由于天然材料中的玻色子通常是弱相互作用和/或寿命短的，因此非常规玻色子物质的创造一直具有挑战性。这个项目通过在半导体莫尔超晶格中使用激子创造非常规玻色子物质来弥补这一差距。与现有的冷原子和量子阱等平台相比，该平台提供了更高的数量级的温度尺度（几十开尔文vs 1开尔文）和可扩展性（10000粒子vs ~100粒子）。研究被纳入“科学作为乐高游戏”主题下的广泛推广计划。利用光学装置的乐高式性质，综合外展活动针对不同教育水平的学生，揭开量子科学的神秘面纱，并向他们介绍潜在的职业选择。具体的活动包括设计一个基于高中实验的光学模块构建系列课程和一个关于量子科学中的光学的周六课程；启动本科生暑期科研实习项目；为研究生和博士后组织量子科学暑期学校。技术摘要：凝聚态物理学旨在理解相互作用如何赋予简单的基本粒子构建块复杂的紧急现象。费米电子的奇异量子相已经在固态系统中得到了深入的研究，包括最近在莫尔维尔超晶格中。然而，由于缺乏合适的凝聚态平台和实验探针，集体玻色子态仍然是超冷原子的范围。该项目旨在克服这两个挑战，并在半导体moir<s:1>超晶格中建立激子-由紧密结合的电子-空穴对组成的玻色子-作为工程相互作用玻色子的奇异集体状态的平台。首席研究员正在开发一套新颖的泵探针光谱，可以直接测量激子的可压缩性，隔离激子的低能“电荷”和“自旋”激发，并研究它们的动力学。这使得识别和研究大量的外来玻色相，如玻色子维格纳晶体、莫特-超流体跃迁、谷伪自旋交换相互作用和伪自旋序等成为可能。该项目开辟了一条通往新型“量子外子材料”的道路，在这种材料中，强相关玻色子产生了奇异的性质和新颖的器件概念，从而与广泛研究的量子电子材料一起建立了凝聚态物质的新基本支柱。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。

Non-technical abstract:Fundamental particles can be classified into fermions and bosons, which have distinct collective behaviors. Interactions between electrons, a fermion, results in now well known emergent properties. On the other hand, creation of unconventional bosonic matter has been challenging since bosons in natural materials are often weakly-interacting and/or short-lived. This project bridges this gap by creating unconventional bosonic matter using excitons in semiconducting moiré superlattices. Compared to existing platforms such as cold atoms and quantum wells, this platform offers orders-of-magnitude higher temperature scale (tens of Kelvin vs. 1 Kelvin) and scalability (10000 particles vs. ~100 particles). Research is incorporated into a broad outreach plan under the theme of “Science as a Lego game”. Leveraging the Lego-like nature of optical setups, integrated outreach activities are targeted at students at many educational levels to demystify quantum science and introduce them to potential career options. Specific activities include designing a high-school lab-based class series on building optical modules and a Saturday class on optics in quantum science; initiating a summer research intern program for undergraduate students; and organizing a quantum science summer school for graduate students and postdocs.Technical abstract:Condensed matter physics aims to understand how interactions endow simple elementary particle building blocks with complex emergent phenomena. Exotic quantum phases of fermionic electrons have been intensively studied in solid-state systems, including recently in moiré superlattices. However, collective bosonic states have remained the purview of ultra-cold atoms due to the lack of suitable condensed matter platforms and experimental probes. This project aims to overcome both challenges and establishe excitons in semiconducting moiré superlattices -- bosons composed of tightly bound electron-hole pairs -- as a platform for engineering exotic collective states of interacting bosons. The principal investigator is developing a set of novel pump- probe spectroscopies that enables direct measurement of exciton compressibility, isolating low energy “charge” and “spin” excitations of excitons, as well as investigating their dynamics. This allows identification and investigation of a plethora of exotic bosonic phases such as bosonic Wigner crystal, Mott-superfluid transition, valley pseudospin exchange interactions and pseudospin orders, etc. This project forges a path to a new class of “quantum exitonic materials” where exotic properties and novel device concepts arise from strongly correlated bosons, thereby establishing a new fundamental pillar of condensed matter alongside the extensively studied quantum electronic materials.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.