Simulating Quantum Frustrated System by a Bose-Einstein Condensated Gas at Negative Temperature

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K14422
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Ozawa Hideki 国立研究開発法人理化学研究所, 量子コンピュータ研究センター, 特別研究員 (50826013)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 冷却原子 / ボース気体 / 超流動 / モット絶縁体 / 三角格子 / 量子気体顕微鏡

Outline of Final Research Achievements

In this research project, we have realized a Bose-Einstein Condensate (BEC) of 87Rb atoms and measured the interference patterns and fillings of the BEC in a triangular optical lattice using a Quantum Gas Microscope (QGM).
The generation of a BEC has been a significant issue in our experimental system. To solve this problem, we introduced an optical trap called a dimple trap, and as a result, the formation of a BEC was confirmed. It is also necessary to coexist a shallow optical lattice where the SF-MI transition occurs and a deep optical lattice for QGM observation. We installed log-scale PDs to achieve a dynamic range of 4 orders of magnitude to overcome this issue.
After the above improvements, we introduced the BEC in the shallow triangular optical lattice and observed that interference peaks appeared at positions corresponding to the reciprocal lattice vectors. Furthermore, we achieved an MI phase of about 80% filling in a deeper lattice.

Free Research Field

物理学

Academic Significance and Societal Importance of the Research Achievements

SF-MI転移の観測は、光格子中の冷却原子を用いた量子シミュレーターとしてのベンチマークテストをクリアしたことになる。n=1のユニットフィリングが準備できたことで、より高度な物理現象を探求するための下地ができたと言える。さらに、三角光格子中のBECとQGMを組み合せることで、TOF測定とin-situ測定の両立が可能になった。これにより、空間的な相分離の可能性まで含めて量子フラストレーション系の相図をより正確に描けるようになった点で、本研究成果は学術的に意義深いと考える。