Inelastic Light Scattering in the Vicinity of a Single-Atom Quantum Point Contact in a Plasmonic Picocavity
arxiv(2023)
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.
更多查看译文
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要