Elucidating the carrier density at which strongly bound excitons dissociate into a plasma of uncorrelated electron-hole pairs is a central topic in the many-body physics of semiconductors. However, there is a lack of information on the high-density response of excitons absorbing in the near-to-mid ultraviolet, due to the absence of suitable experimental probes in this elusive spectral range. Here, we present a unique combination of many-body perturbation theory and state-of-the-art ultrafast broadband ultraviolet spectroscopy to unveil the interplay between the ultraviolet-absorbing two-dimensional excitons of anatase TiO$_2$ and a sea of electron-hole pairs. We discover that the critical density for the exciton Mott transition in this material is the highest ever reported in semiconductors. These results deepen our knowledge of the exciton Mott transition and pave the route toward the investigation of the exciton phase diagram in a variety of wide-gap insulators.
Dimensionality-Dependent Exciton Dispersion in a Single-Band Mott Insulator
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；School of Physics, Zhejiang University（浙江大学物理学院）；State Key Laboratory of Silicon and Advanced Semiconductor Materials, Zhejiang University（浙江大学硅酸盐先进半导体材料国家重点实验室）；School of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China（中国人民大学物理学院及光电功能材料与微纳器件北京市重点实验室）；Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China（中国人民大学量子态构建与操控教育部重点实验室）；International Center for Quantum Materials, and Electron Microscopy Laboratory, School of Physics, Peking University（北京大学物理学院国际量子材料中心及电子显微镜实验室）；Department of Physics, Fuzhou University（福州大学物理系）
Excitons probe intrinsic flat band Mottness in a van der Waals heterostructure
Peking University（北京大学）；Academy for Advanced Interdisciplinary Studies, Peking University（北京大学前沿交叉学科研究院）；The University of Hong Kong（香港大学）；University of Chinese Academy of Sciences（中国科学院大学）；HK Institute of Quantum Science & Technology, The University of Hong Kong（香港大学量子科学与技术研究所）；Zhengzhou University（郑州大学）；National Institute for Materials Science（物质材料研究机构）；Liaoning Academy of Materials（辽宁省材料科学研究院）；ShanghaiTech University（上海科技大学）；South China Normal University（华南师范大学）；Songshan Lake Materials Laboratory（松山湖材料实验室）
Lattice correlation of Hubbard excitons in a Mott insulator Sr2IrO4 and reconstruction of their hopping dynamics via time-dependent coherence analysis of the Bragg diffraction
Excitons versus electron-hole plasma in monolayer transition metal dichalcogenide semiconductors
当电子-空穴对在半导体中被激发时，先验地不清楚它们是否形成未结合粒子的费米子等离子体或玻色子激子气体。通常，激子相与低温相关联。在原子薄的过渡金属二硫属化物半导体中，激子由于强库仑相互作用和大的激子态密度而即使在室温下也是特别重要的。使用国家的最先进的多体理论，包括动态屏蔽，我们表明，激子与等离子体的比例可以有效地调整介电基板屏蔽以及载流子掺杂。此外，我们预测莫特过渡从激子占主导地位的制度完全电离的电子-空穴等离子体之间的激发密度$3\times10^{12}$ cm $^{-2}$和$1\times10^{13}$ cm $^{-2}$取决于温度，载流子掺杂和介电环境。我们建议通过研究激子卫星光电子能谱和扫描隧道显微镜观察这些影响。
Exciton pairs coupled via the long-living phonons and their superfluorescent markers
Institute for Advanced Study in Mathematics, Harbin Institute of Technology（哈尔滨工业大学高等研究院）；Suzhou Research Institute, Harbin Institute of Technology（哈尔滨工业大学苏州研究院）；Faculty of Science, H.I.T.-Holon Institute of Technology（希伯来-霍隆理工学院理学院）
