CAREER: Probing exciton-exciton correlations and phase transitions for spin-polarized excitons in monolayer transition metal dichalcogenides

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。当光被固体吸收时，它可以产生一种瞬态激发准粒子，即所谓的激子，它同时携带光和物质的信息。了解激子相互作用对于未来设计无接触、全光控制和传感的量子器件至关重要。该项目研究了原子薄二维晶体中激子之间的量子相关性，具有异常强的光-物质相互作用。二维晶体独特的光学和电子特性使量子相关的实现有望远高于液氦温度。该研究成果将为未来量子技术的发展建立新的平台系统，以实现片上操作和相干控制。该项目与研究相结合，旨在通过跨学科的研究项目和任务，促进女性参与STEM，培养下一代STEM劳动力。佛罗里达大学将为STEM领域的女性组织一系列职业支持研讨会。此外，将开发光学科学示范站，在当地博物馆展示，以提高年轻一代的STEM意识。该项目由材料研究部（DMR）的凝聚态物理（CMP）和电子与光子材料（EPM）项目共同资助。技术摘要激子是一种束缚电子-空穴对，可以被认为是玻色子，通常通过半导体中的光激发产生。几十年来，在稀激子气体极限之外，激子-激子相关形式以及实现激子液相和凝聚态量子简并的可能性引起了人们的极大关注。最近，过渡金属二硫族化合物二维半导体的出现为激子物理学提供了一个全新的范例，其中激子具有异常强的结合能，并且可以全光控制自旋和谷自由度。本项目旨在研究钨基单层过渡金属二硫化物中非线性激子相互作用，并寻求激子复合物相关的实验特征。特别是，本研究将侧重于具有长寿命和支持高激子密度的自旋极化激子态。通过超快光谱学和光电子探针的结合，研究了二维激子的经典态和可能的量子简并。该结果将有助于我们对二维激子多体相互作用的理解，并为实现紧凑二维器件的宏观相干性奠定基础。对这些自旋极化激子的研究也将阐明玻色子的自旋极化如何影响相关的形成和进一步的宏观相干性。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Non-technical abstract When light is absorbed by a solid, it can create a transient excitation quasiparticle, the so-called exciton, which carries information from both the light and the matter. Understanding excitonic interactions are crucial for the future design of quantum devices with contact-free, all-optical control and sensing. This project investigates the quantum correlations between excitons in an atomically-thin two-dimensional crystal with exceptionally strong light-matter interactions. The unique optical and electronic properties of the two-dimensional crystal promise the realization of quantum correlation well above the liquid helium temperature. The research results will establish new platform systems to achieve on-chip operation and control of coherence for future quantum technology developments. Integrated with the research, the project aims to promote the participation of women in STEM and train the next-generation STEM workforce through interdisciplinary research projects and tasks. A series of career support seminars for women in STEM will be organized at the University of Florida. In addition, optics science demonstration stations will be developed for display in a local museum to increase STEM awareness in a younger generation.This project is jointly funded by the Condensed Matter Physics (CMP) and the Electronic and Photonic Materials (EPM) programs of the Division of Materials Research (DMR).Technical abstract An exciton is a bound electron-hole pair that can be considered as a Boson, often created through optical excitations in semiconductors. Beyond the dilute exciton gas limit, exciton-exciton correlation forms, and the possibility of achieving quantum degeneracy of exciton liquid and condensate phases have attracted great attention for decades. The recent advent of two-dimensional (2D) semiconductors of transition metal dichalcogenides provides a completely new paradigm for exciton physics, where excitons have anomalously strong binding energy and enable all-optical control of the spin and valley degrees of freedom. This project aims to investigate the nonlinear exciton interactions and seek experimental signatures of exciton complex correlations in tungsten-based monolayer transition metal dichalcogenides. In particular, this research will focus on spin-polarized excitonic states, which have long lifetimes and support a high exciton density. Both the classical regime and the possible quantum degeneracy of 2D excitons will be investigated through a combination of ultrafast optical spectroscopies and optoelectronic probes. The outcome will inform our understanding of excitonic many-body interactions in 2D and lay the foundation for realizing macroscopic coherence in compact 2D devices. Investigation of these spin-polarized excitons will also elucidate how the spin polarization of bosons affects the formation of correlation and further macroscopic coherence.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.