Antonio Rossi*, Jonas Zipfel, Indrajit Maity, Monica Lorenzon, Medha Dandu, Elyse Barré, Luca Francaviglia, Emma C. Regan, Zuocheng Zhang, Jacob H. Nie, Edward S. Barnard, Kenji Watanabe, Takashi Taniguchi, Eli Rotenberg, Feng Wang, Johannes Lischner, Archana Raja* and Alexander Weber-Bargioni*,
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引用次数: 0
Abstract
Stacking van der Waals crystals allows for the on-demand creation of a periodic potential landscape to tailor the transport of quasiparticle excitations. We investigate the diffusion of photoexcited electron–hole pairs, or excitons, at the interface of WS2/WSe2 van der Waals heterostructure over a wide range of temperatures. We observe the appearance of distinct interlayer excitons for parallel and antiparallel stacking and track their diffusion through spatially and temporally resolved photoluminescence spectroscopy from 30 to 250 K. While the measured exciton diffusivity decreases with temperature, it surprisingly plateaus below 90 K. Our observations cannot be explained by classical models like hopping in the moiré potential. A combination of ab initio theory and molecular dynamics simulations suggests that low-energy phonons arising from the mismatched lattices of moiré heterostructures, also known as phasons, play a key role in describing and understanding this anomalous behavior of exciton diffusion. Our observations indicate that the moiré potential landscape is dynamic down to very low temperatures and that the phason modes can enable efficient transport of energy in the form of excitons.
通过堆叠范德瓦耳斯晶体,可以按需创建周期性电势图,从而调整准粒子激发的传输。我们研究了 WS2/WSe2 范德瓦尔斯异质结构界面上光激发电子-空穴对或激子在宽温度范围内的扩散情况。我们观察到平行堆叠和反平行堆叠出现了不同的层间激子,并通过空间和时间分辨光致发光光谱跟踪它们在 30 至 250 K 范围内的扩散情况。结合 ab initio 理论和分子动力学模拟表明,摩尔异质结构的不匹配晶格(也称为 phasons)产生的低能声子在描述和理解这种异常的激子扩散行为中起着关键作用。我们的观察结果表明,摩尔势图在极低温度下也是动态的,而声子模式可以实现激子形式的能量高效传输。
期刊介绍:
ACS Nano, published monthly, serves as an international forum for comprehensive articles on nanoscience and nanotechnology research at the intersections of chemistry, biology, materials science, physics, and engineering. The journal fosters communication among scientists in these communities, facilitating collaboration, new research opportunities, and advancements through discoveries. ACS Nano covers synthesis, assembly, characterization, theory, and simulation of nanostructures, nanobiotechnology, nanofabrication, methods and tools for nanoscience and nanotechnology, and self- and directed-assembly. Alongside original research articles, it offers thorough reviews, perspectives on cutting-edge research, and discussions envisioning the future of nanoscience and nanotechnology.