等离子体皮腔中单原子量子点接触附近的非弹性光散射
Inelastic Light Scattering in the Vicinity of a Single-Atom Quantum Point Contact in a Plasmonic Picocavity
AI总结：
本研究结合低温光学STM实验与含时密度泛函理论，揭示皮腔中单原子QPC形成时原子结构弛豫对等离子体场和TERS振动信号的突变影响。
摘要：
在此，我们利用低温光学扫描隧道显微镜（STM）研究了单原子量子点接触（QPC）附近的非弹性光散射（ILS）。在ILS光谱中分辨出一种局域于Ag(111)表面单个Ag吸附原子的振动模式，这是由STM结中原子级受限等离子体场产生的针尖增强拉曼散射（TERS）所致。此外，我们追踪了来自单个吸附原子的TERS如何随间隙距离演化。低温STM出色的稳定性使我们能够考察皮腔明显不同的电子输运区，即隧穿区和量子点接触（QPC）区。该测量表明，局域于吸附原子的振动模式及其TERS强度在QPC形成时表现出急剧变化，表明原子级结构对等离子体性质具有关键影响。为了从微观上深入理解皮腔光力学，我们利用含时密度泛函理论仔细考察了STM结中的结构和等离子体场。模拟揭示，单原子QPC处的原子尺度结构弛豫导致等离子体场强度、体积和分布以及局域于单个原子的振动模式发生离散变化。这些发现对实验观测给出了定性解释。此外，我们通过连续形成、断开和重新形成原子接触，证明强ILS是QPC的一个特征，并展示了等离子体共振在非隧穿、隧穿和QPC各区域中如何演化。
英文摘要：
Here, using low-temperature optical scanning tunneling microscopy (STM), we investigate inelastic light scattering (ILS) in the vicinity of a single-atom quantum point contact (QPC). A vibration mode localized at the single Ag adatom on the Ag(111) surface is resolved in the ILS spectrum, resulting from tip-enhanced Raman scattering (TERS) by the atomically-confined plasmonic field in the STM junction. Furthermore, we trace how TERS from the single adatom evolves as a function of the gap distance. The exceptional stability of the low-temperature STM allows to examine distinctly different electron transport regimes of the picocavity, namely in the tunneling and quantum point contact (QPC) regimes. This measurement shows that the vibration mode localized at the adatom and its TERS intensity exhibits a sharp change upon the QPC formation, indicating that the atomic-level structure has a crucial impact on the plasmonic properties. To gain microscopic insights into picocavity optomechanics, we scrutinize the structure and plasmonic field in the STM junction using time-dependent density functional theory. The simulations reveal that atomic-scale structural relaxation at the single-atom QPC results in a discrete change of the plasmonic field strength, volume, and distribution as well as the vibration mode localized at the single atom. These findings give a qualitative explanation for the experimental observations. Furthermore, we demonstrate that strong ILS is a characteristic feature of QPC by continuously forming, breaking, and reforming the atomic contact, and how the plasmonic resonance evolves throughout the non-tunneling, tunneling, and QPC regimes.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
