少层黑磷量子阱子带间跃迁的红外光谱研究

The energy bands of solids are quantized to form subbands under quantum confinement. The infrared optoelectronic devices based on the intersubband transitions of quantum wells have been widely used in national defense, industry and daily lives. Mechanical exfoliation can produce high quality few-layer black phosphorus quantum wells. Such quantum wells are atomically thin and show almost no thickness fluctuations for individual wells. Quantum many-body effect, such as plasmonic effect and exciton-like effect, becomes apparent in black phosphorus quantum wells. In this project, we utilize infrared spectroscopy to interrogate the intersubband transitions in few-layer black phosphorus quantum wells, with particular emphasis on the layer-dependence, Fermi-level dependence and temperature dependence of such transitions. We hope to realize the in-situ tuning of the many-body effect. Our work can determine the basic electronic structures of few-layer black phosphorus and paves the way for its application in infrared optoelectronics.

量子受限效应使能带量子化而形成子带。基于量子阱子带间跃迁的红外光电器件在国防和生活生产中被广泛应用。通过机械剥离法可以制备高质量少层黑磷量子阱。这种新型量子阱厚度达到原子层级别且单个量子阱中几乎无厚度涨落。诸如等离激元效应和类激子效应的量子多体效应在少层黑磷量子阱中会较为明显。本项目将用红外光谱手段研究少层黑磷量子阱的子带间跃迁，系统考察子带间跃迁频率和强度等特征与黑磷层数、费米能级和温度的依赖关系，实现对子带间跃迁量子多体效应的有效调控；确定少层黑磷的基本能带结构，为其在红外光电器件中的应用奠定基础。

层状半导体黑磷无论厚薄都是直接带隙半导体，并且由于层间耦合强，黑磷的带隙随厚度有明显变化，这些有利条件使黑磷成为了性能优异的范德瓦尔斯量子阱。然而，人们对少层黑磷的子带结构了解甚少。本项目利用红外光谱技术探测黑磷量子阱本征的子带能带结构，并利用应变、压强、温度和电场等手段调控能带。我们首次观测到一系列新的禁戒跃迁；揭示了黑磷激子“以少胜多”的反常吸收能力；发现应变、压强和温度可以有效调节黑磷的层间耦合，从而方便地调控子带结构。相关研究成果发表在Nature Communications (3篇)、Physical Review Letters(2篇)等杂志。