Zhang Guowei, Huang Shenyang, Chaves Andrey, Yan Hugen
Institute of Flexible Electronics, Northwestern Polytechnical University, Xi'an 710072, Shaanxi, China.
Department of Physics, State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China.
ACS Nano. 2023 Mar 28;17(6):6073-6080. doi: 10.1021/acsnano.3c00904. Epub 2023 Mar 13.
Van der Waals quantum wells, naturally formed in two-dimensional layered materials with nanoscale thickness, possess many inherent advantages over conventional molecular beam epitaxy grown counterparts, and could bring up intriguing physics and applications. However, optical transitions originated from the series of quantized states in these emerging quantum wells are still elusive. Here, we show that multilayer black phosphorus appears to be an excellent candidate for van der Waals quantum wells with well-defined subbands and high optical quality. Using infrared absorption spectroscopy, we probe subband structures of multilayer black phosphorus with tens of atomic layers, revealing clear signatures for optical transitions with subband index as high as 10, far from what was attainable previously. Surprisingly, in addition to allowed transitions, an unexpected series of "forbidden" transitions is also evidently observed, which enables us to determine energy spacings separately for conduction and valence subbands. Furthermore, the linear tunability of subband spacings by temperature and strain is demonstrated. Our results are expected to facilitate potential applications for infrared optoelectronics based on tunable van der Waals quantum wells.
范德华量子阱自然形成于具有纳米级厚度的二维层状材料中，与传统分子束外延生长的量子阱相比具有许多固有优势，并且可能带来引人入胜的物理现象和应用。然而，源自这些新兴量子阱中一系列量子化状态的光学跃迁仍然难以捉摸。在此，我们表明多层黑磷似乎是具有明确子带和高光学质量的范德华量子阱的极佳候选材料。利用红外吸收光谱，我们探测了具有数十个原子层的多层黑磷的子带结构，揭示了子带指数高达10的光学跃迁的清晰特征，这远远超出了之前所能达到的范围。令人惊讶的是，除了允许的跃迁之外，还明显观察到了一系列意想不到的“禁戒”跃迁，这使我们能够分别确定导带子带和价带子带的能量间距。此外，还展示了子带间距随温度和应变的线性可调性。我们的结果有望促进基于可调谐范德华量子阱的红外光电子学的潜在应用。
