Electron-phonon coupled systems with phononic crystal resonators

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K18751
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Fujisawa Toshimasa 東京工業大学, 理学院, 教授 (20212186)
• Project Period (FY): 2017-06-30 – 2023-03-31
• Keywords: 電子フォノン結合系 / フォノニック結晶共振器 / 量子ナノデバイス

Outline of Final Research Achievements

The objective of the project is to provide coherently coupled electron-phonon systems by taking advantage of electron-phonon interactions in semiconductors. Such coupled systems might be able to minimize the decoherence issues of electron systems. The system can be prepared by designing phononic band structures and phonon resonators for surface acoustic waves and embedding a mesoscopic electronic system inside the resonator. In practice, periodic patterns of a metal film are formed on a surface of an AlGaAs/GaAs modulation doped heterostructure to develop a double quantum dot in a phonon resonator. For example, a two-electron double quantum dot in the Pauli spin blockade regime was formed to study spin-conserved and spin-flip phonon-assisted tunneling. We successfully observed phonon-induced Rabi splitting by analyzing the spin-flip phonon-assisted transport characteristics. This would provide a novel opportunity for studying novel electron-phonon coupled systems in the future.

Free Research Field

メゾスコピック系

Academic Significance and Societal Importance of the Research Achievements

通常、電子格子相互作用によるフォノン散乱は、電子系のコヒーレンスを乱す悪役としての印象が強い。本研究では、電子格子相互作用を積極的に活用し、電子と格子が結合した１つの系として扱うことで、フォノン散乱によるデコヒーレンスなどの問題点を克服し、電子格子結合系全体の量子性に着目するという新たな視点での研究を進めた。これは、電子フォノン結合系での共振器量子電磁力学の創生を目指すもので、その学問的な価値は非常に高い。本研究では、フォノン励起によるラビ分裂の観測により、一定の成果に達したものと考えている。今後、素子構造の改善などで真空ラビ分裂の観測に至ると、より学術的・社会的価値が明確になると期待する。