Dark excitons: Energetics, dynamics, transport and correlated phases

暗激子：能量学、动力学、输运和相关相

• 批准号: 535247173
• 负责人: Professor Dr. Stefan Mathias
• 金额: --
• 依托单位: I. Physikalisches Institut - Festkörper- und Tieftemperaturphysik -
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/535247173?language=en
• 关键词: Dark; excitons; Energetics; dynamics; transport

We aim to explore the energetics, dynamics, transport properties and correlated interactions of intralayer, hybrid and interlayer excitons in two-dimensional semiconductors. While experimental research in this direction is well established, our project provides a complementary and powerful approach to open research questions: In our preliminary work, we have developed a new generation time- and angle-resolved photoemission spectroscopy (trARPES) experiment that can be applied to exfoliated and artificially stacked van-der-Waals heterostructures; the formation and thermalization dynamics of bright and dark excitons can be accessed on ultrashort time- and length-scales (55 fs time-, 150 meV energy-, 0.04 1/A momentum- and 500 nm spatial-resolution). In the SPP, we will make use of the full capabilities of trARPES to study the spatio-temporal dynamics of bright and dark excitons in exfoliated heterostructures of transition metal dichalcogenides (TMDs). Specifically, by tuning the moiré wavelength (i.e., the twist-angle), by suppressing interlayer hybridization by hexagonal boron nitride (hBN) decoupling layers and by creating local strain gradients, we aim to control the dynamics and correlated interactions of excitons in space and time. We will focus on three objectives: First (i), we will study the impact of exciton confinement and flat band physics onto the formation and thermalization dynamics of bright and dark excitons in TMD/TMD and TMD/hBN/TMD heterostructures. Second (ii), in order to experimentally characterize diffusion processes of bright and dark excitons, we will monitor the spatio-temporal exciton dynamics in the presence of the moiré potential, hBN decoupling layers and local strain gradients. And third (iii), we will investigate the creation and stabilization of dark exciton condensates in TMD/hBN/TMD heterostructures. Beyond the established experimental approaches, we will make use of momentum-resolved photoemission technique and orbital tomography in order to study exciton condensates from the perspective of the exciton’s real-space wavefunction.

我们的目标是探索二维半导体中层内、混合和层间激子的能量学、动力学、输运特性和相关相互作用。虽然这个方向的实验研究已经很成熟，但我们的项目为开放研究问题提供了一种补充和强大的方法：在我们的前期工作中，我们开发了新一代时间和角度分辨光电子能谱（trARPES）实验，可应用于剥离和人工堆叠的范德华异质结构的形成和热化；我们将在超短时间和长度尺度（55 fs 时间、150 meV 能量、0.04 1/A 动量和 500 nm 空间分辨率）上获取明激子和暗激子的动力学。 trARPES 研究过渡金属二硫化物剥离异质结构中明激子和暗激子时空动力学的全部功能具体来说，通过调节莫尔波长（即扭转角）、通过六方氮化硼（hBN）去耦层抑制层间杂化以及创建应变局部梯度，我们的目标是控制动力学和相关相互作用。我们将重点关注三个目标：首先，我们将研究激子限制和平带物理对亮和暗的形成和热化动力学的影响。第二(ii)，为了通过实验表征明激子和暗激子的扩散过程，我们将监测莫尔势、hBN 去耦存在下的时空激子动力学。第三，我们将研究 TMD/hBN/TMD 异质结构中暗激子凝聚的产生和稳定。在已建立的实验方法的基础上，我们将利用动量分辨光电子技术和轨道层析成像技术，从激子的实空间波函数的角度研究激子凝聚态。