范德华异质结构中的层间暗激子
Interlayer dark excitons in a van der Waals heterostructure
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中文总结 AI 辅助
本研究通过光谱直接识别WSe2/hBN/WSe2同质双层中的亮和暗层间激子，发现暗激子具有超长寿命和强谷极化，并展示了扭转角对激子发射的调控，为TMD异质结构激子物理与器件应用提供关键见解。
中文摘要 AI 辅助
过渡金属二硫属化物（TMD）异质结构中的层间激子具有长寿命和长程输运特性，使其有望用于激子器件和量子多体相（如玻色-爱因斯坦凝聚）。实现这些目标需要精确理解自旋允许的亮激子和名义上自旋禁止的暗激子，因为最低能量的激子种类决定了粒子数、输运和凝聚行为。尽管已取得重大进展，但明确区分单重态和三重态层间激子仍具挑战性，因为这类异质结构中的莫尔激子可能模拟其光学特征。在此，我们报告了在高质量、双栅极WSe2/hBN/WSe2同质双层中，对亮（单重态）和暗（三重态）层间激子的直接光谱识别。电场依赖的光致发光和反射谱揭示了两个具有不同自旋构型的动量直接层间跃迁。层间暗激子遵循与亮激子不同的选择定则。引人注目的是，层间暗激子即使在超过微秒的超长寿命下仍保持强谷极化。最后，我们展示了扭转角控制，其中扭转诱导的电子-空穴动量失配调节层间激子发射。这些结果为TMD异质结构的电子和激子结构提供了关键见解，为激子多体物理和光电子器件开辟了新途径。
英文摘要
Interlayer excitons in transition metal dichalcogenide (TMD) heterostructures exhibit long lifetimes and long-range transport, making them promising for excitonic devices and quantum many-body phases, such as Bose-Einstein condensates. Achieving these goals requires a precise understanding of spin-allowed bright and nominally spin-forbidden dark excitons, because the lowest-energy exciton species governs population, transport, and condensation. Despite substantial progress, unambiguously distinguishing singlet and triplet interlayer excitons has been challenging, as moiré excitons in these heterostructures can mimic their optical signatures. Here, we report the direct spectroscopic identification of bright (singlet) and dark (triplet) interlayer excitons in high-quality, dual-gated WSe$_2$/hBN/WSe$_2$ homobilayers. Electric-field-dependent photoluminescence and reflectance reveal two momentum-direct interlayer transitions with distinct spin configurations. The interlayer dark excitons obey selection rules that differ from those of bright excitons. Strikingly, interlayer dark excitons retain strong valley polarization, even with their ultralong lifetime exceeding microseconds. Finally, we demonstrate twist-angle control, wherein twist-induced electron-hole momentum mismatch modulates interlayer exciton emission. These results provide critical insights into the electronic and excitonic structure of TMD heterostructures, opening new avenues for excitonic many-body physics and optoelectronic devices.
发表机构
- University of Maryland（马里兰大学）
- Brookhaven National Laboratory（布鲁克海文国家实验室）
- National Institute for Materials Science（国立材料研究所）
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