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

低温扫描隧道显微镜（STM）用于在半导体表面上创建人工量子结构，并通过扫描隧道光谱（STS）探索其电子特性。为了创建这种结构，我们开发了一种高度可控的方式在InAs（111）A表面上进行原子操作。原始InAs（111）A具有表面态和低覆盖率的原生In吸附原子。吸附原子带正电荷，可以通过STM针尖重新定位，从而可以设计静电势景观，并在原子长度尺度上以原子精度诱导载流子约束。我们证明，单量子点和量子点分子具有完美定义的能级结构可以通过这种方式创建。我们还构建了二聚量子点链，揭示了位于末端和内部畴壁的电子态，与Su-Schrieffer-Heeger（SSH）模型预测的拓扑边界态一致。在我们以前工作的基础上，我们计划在新的项目期间解决三个主要目标（主题领域）：（i）深入分析和全面描述量子点分子的能级结构，说明超越简单s轨道紧束缚模型的杂化效应。(ii)在（110）解理的InAs表面上扩展人工量子点组装，后者提供了更大的平台尺寸，因此可以构建更扩展的结构，如Kagomé晶格和SSH模型的二维类似物。(iii)STM/STS和原子操纵（110）-解理III-V半导体异质结构的带边设计，涉及宽带隙层嵌入窄带隙层;我们预计，这一专题领域的结果将奠定基础，为未来的研究，旨在实现外部电极，使STM产生的量子结构的电门控。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减小的维度中的行为的详细了解。这一发现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.