Quantum Optics on Phonons in Carbon Nanotube

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K14637
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Meiji University
• Principal Investigator: Okuyama Rin 明治大学, 理工学部, 助教 (60735562)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: カーボンナノチューブ / 機械的運動 / 格子振動 / フォノン / 群の表現論 / トポロジカル絶縁体 / キャビティQED / 剛体回転の量子論

Outline of Final Research Achievements

In this study, we have theoretically examined the quantum natures of the mechanical motions of carbon nanotubes (CNTs). First, we have constructed a group-theory framework for the perpendicular phonons, which transform just in the same manner as electrons for the symmetric operations. The Dirac dispersion relation and the curvature-induced fine structures have been predicted for the phonons. Then, we have examined a phonon-based cavity QED (Quantum ElectroDynamics), where a charged qubit embedded in a CNT couples to its localized phonon mode. This is nothing but the situation realized in a conventional cavity QED, but the Fermion-Boson coupling is much larger than in the optical counterpart. The strong coupling manifests itself as the Franck-Condon effect. Finally, the rigid-body rotation have been studied. We have shown that the quantum states of a CNT confined in a bearing potential can be identified to the classical rotation modes, the pure rotation, precession, and nutation.

Free Research Field

理論物性物理学

Academic Significance and Societal Importance of the Research Achievements

本研究ではカーボンナノチューブの機械的運動の量子論な性質を理論的に調べた。従来、ナノチューブの物性研究はその特異な電子系を主たる対象としており、機械運動そのものに着目した研究は稀である。ナノチューブはエレクトロニクスだけでなく、強靱かつ軽量なワイヤとしての応用も期待されており、基礎研究の分野からの下支えは重要である。さらに、ナノチューブのようなセミマクロな物体の量子状態の研究は、系のスケール変化によって、どのように量子系から古典系へのクロスオーバーが起きるのかという量子力学の根源的な問いを考える上で重要なヒントとなるだろう。