CAREER: Correlated Excitons in Semiconducting Moire Superlattices

非技术摘要：基本粒子可以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是一种费米子，导致了现在众所周知的浮现性质。另一方面，非传统玻色子的创造一直是具有挑战性的，因为天然材料中的玻色子通常是弱相互作用和/或短暂的。这个项目通过在半导体莫尔超晶格中使用激子创造非传统的玻色子物质来弥合这一差距。与冷原子和量子阱等现有平台相比，该平台提供了更高数量级的温度标度(数十开尔文对1开尔文)和可扩展性(10000粒子对约100粒子)。研究纳入了一项广泛的外联计划，其主题是“作为乐高游戏的科学”。利用光学设置的乐高性质，综合外展活动针对许多教育级别的学生，以揭开量子科学的神秘面纱，并向他们介绍潜在的职业选择。具体活动包括设计一个关于构建光学模块的高中实验系列课程和一个关于量子科学光学的周六课程；为本科生启动一个暑期研究实习生计划；为研究生和博士后组织一个量子科学暑期班。技术摘要：凝聚态物理旨在了解相互作用如何赋予简单的基本粒子积木复杂的浮现现象。费米子电子的奇异量子相在固体系统中得到了广泛的研究，包括最近在莫尔超晶格中的研究。然而，由于缺乏合适的凝聚态平台和实验探测器，集体玻色态仍然是超冷原子的研究范围。该项目旨在克服这两个挑战，并在半导体莫尔超晶格--由紧密束缚的电子-空穴对组成的玻色子--中建立激子，作为设计相互作用玻色子的奇异集体态的平台。首席研究人员正在开发一套新型的泵浦-探测光谱仪，能够直接测量激子的可压缩性，分离激子的低能“电荷”和“自旋”激发，并研究它们的动力学。这使得可以识别和研究过多的奇异玻色子相，如玻色子Wigner晶体、Mott-超流体转变、谷伪自旋交换相互作用和伪自旋有序等。该项目开辟了一条通往新类别的“量子激子材料”的道路，其中奇异性质和新颖的装置概念产生于强关联玻色子，从而与广泛研究的量子电子材料一起建立了一个新的凝聚态基本支柱。这一奖项反映了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。

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.