Biswas Souvik, Wong Joeson, Pokawanvit Supavit, Yang Wei-Chang David, Zhang Huairuo, Akbari Hamidreza, Watanabe Kenji, Taniguchi Takashi, Davydov Albert V, da Jornada Felipe H, Atwater Harry A
Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States.
Department of Applied Physics, Stanford University, Stanford, California 94305, United States.
ACS Nano. 2023 Dec 12;17(23):23692-23701. doi: 10.1021/acsnano.3c07337. Epub 2023 Oct 20.
Quantum confinement of two-dimensional excitons in van der Waals materials via electrostatic trapping, lithographic patterning, Moiré potentials, and chemical implantation has enabled significant advances in tailoring light emission from nanostructures. While such approaches rely on complex preparation of materials, natural edges are a ubiquitous feature in layered materials and provide a different approach for investigating quantum-confined excitons. Here, we observe that certain edge sites of monolayer black phosphorus (BP) strongly localize the intrinsic quasi-one-dimensional excitons, yielding sharp spectral lines in photoluminescence, with nearly an order of magnitude line width reduction. Through structural characterization of BP edges using transmission electron microscopy and first-principles GW plus Bethe-Salpeter equation (GW-BSE) calculations of exemplary BP nanoribbons, we find that certain atomic reconstructions can strongly quantum-confine excitons resulting in distinct emission features, mediated by local strain and screening. We observe linearly polarized luminescence emission from edge reconstructions that preserve the mirror symmetry of the parent BP lattice, in agreement with calculations. Furthermore, we demonstrate efficient electrical switching of localized edge excitonic luminescence, whose sites act as excitonic transistors for emission. Localized emission from BP edges motivates exploration of nanoribbons and quantum dots as hosts for tunable narrowband light generation, with future potential to create atomic-like structures for quantum information processing applications as well as exploration of exotic phases that may reside in atomic edge structures.
通过静电捕获、光刻图案化、莫尔势和化学注入在范德华材料中实现二维激子的量子限制，已在定制纳米结构的发光方面取得了重大进展。虽然这些方法依赖于复杂的材料制备，但天然边缘是层状材料中普遍存在的特征，并为研究量子限制激子提供了一种不同的方法。在这里，我们观察到单层黑磷（BP）的某些边缘位点强烈地局域化了本征准一维激子，在光致发光中产生尖锐的光谱线，线宽减小了近一个数量级。通过使用透射电子显微镜对BP边缘进行结构表征以及对示例性BP纳米带进行第一性原理GW加贝塞耳-萨尔皮特方程（GW-BSE）计算，我们发现某些原子重构可以强烈地量子限制激子，从而产生由局部应变和屏蔽介导的独特发射特征。我们观察到边缘重构发出的线性偏振发光，其保留了母体BP晶格的镜像对称性，这与计算结果一致。此外，我们展示了局域边缘激子发光的有效电开关，其位点充当发射的激子晶体管。BP边缘的局域发射激发了对纳米带和量子点作为可调谐窄带光产生主体的探索，未来有可能创建用于量子信息处理应用的类原子结构，并探索可能存在于原子边缘结构中的奇异相。
