Artificial quantum states on semiconductor surfaces created and probed by cryogenic scanning tunneling microscopy

低温扫描隧道显微镜(STM)用于在半导体表面产生人工量子结构，并通过扫描隧道谱(STS)研究其电子性质。为了建立这种结构，我们开发了一种在InAs(111)A表面上高度可控的原子操纵方法。原始的InAs(111)A具有表面态和低覆盖率的天然吸附原子。吸附原子是带正电荷的，可以被STM针尖重新定位，这使得在原子长度尺度上和原子精度上设计静电势场和诱导载流子限制成为可能。我们证明了用这种方法可以创造出单量子点和具有完美定义的能级结构的量子点分子。我们还构建了二聚化量子点链，揭示了局域化的电子态在末端和内部磁区壁，这与Su-Schrieffer-Heeger(SSH)模型预测的拓扑边界态是一致的。在我们以前工作的基础上，我们计划在新的项目期内解决三个主要目标(专题领域)：(I)深入分析和全面描述量子点分子的能级结构，考虑到超越简单的S轨道紧束缚模型的杂交效应。(Ii)扩展到(110)解理的InAs表面上的人造量子点组件，后者提供更大的平台尺寸，从而构建更多扩展的结构，如Kagomé晶格和SSH模型的二维类似物。(Iii)STM/STS和原子操纵在(110)裂解的III-V半导体异质结上的带边设计，包括嵌入在窄带隙层中的宽禁带层；我们预计这一专题领域的结果将为未来旨在实现外部电极以实现STM产生的量子结构的电选通的研究奠定基础。在我们的项目中研究的半导体上完美定义和可调的表面结构提供了对电子在降维中的行为的详细洞察。这一见解对基础科学和未来的量子技术都很重要。

Cryogenic scanning tunneling microscopy (STM) is used to create artificial quantum structures on semiconductor surfaces and explore their electronic properties by scanning tunneling spectroscopy (STS). To create the structures, we developed a highly controllable way of atom manipulation on the InAs(111)A surface. Pristine InAs(111)A hosts a surface state and a low coverage of native In adatoms. The adatoms are positively charged and can be repositioned by the STM tip, making it possible to engineer the electrostatic potential landscape and induce carrier confinement on the atomic length scale and with atomic precision. We demonstrated that single quantum dots and quantum-dot molecules with a perfectly defined energy level structure can be created in this way. We also constructed dimerized quantum-dot chains revealing electronic states localized at the ends and at internal domain walls, consistent with topological boundary states predicted by the Su-Schrieffer-Heeger (SSH) model. Building on our previous work, we plan to address three major objectives (topical areas) in the new project period: (i) In-depth analysis and full description of the energy level structure of quantum-dot molecules accounting for hybridization effects that go beyond a simple s-orbital tight-binding model. (ii) Extension to artificial quantum-dot assemblies on the (110)-cleaved InAs surface, the latter offering significantly larger terrace sizes and hence the construction of more extended structures such as Kagomé lattices and two-dimensional analogues of the SSH model. (iii) STM/STS and atom manipulation on (110)-cleaved III-V semiconductor heterostructures with a band-edge design involving wide band gap layers embedded in narrow band gap layers; we anticipate that the results of this topical area will lie the groundwork for future research aiming at the implementation of external electrodes to enable electrical gating of the STM-generated quantum structures. Perfectly defined and tunable surface structures on semiconductors as investigated in our project provide detailed insight into the behavior of electrons in reduced dimensions. This insight is important both for fundamental science and future quantum technologies.