Research to elucidate the formation process of strongly correlated many-body systems using high tunability of ultracold Fermi gas

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03689
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Keio University
• Principal Investigator: Ohashi Yoji 慶應義塾大学, 理工学部(矢上), 教授 (60272134)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 非平衡状態 / 強結合効果 / 量子多体効果 / BCS-BECクロスオーバー / 超流動 / フェルミ原子気体 / 光格子 / 非平衡グリーン関数

Outline of Final Research Achievements

I theoretically studied an interacting two-component Fermi atomic gas, being coupled with two reservoirs having different values of the Fermi chemical potential. In the non-equilibrium steady state, I found that the two reservoirs imprint a two-edge structure on the momentum distribution of Fermi atoms in the BCS-BEC crossover region, leading to the realization of a Fulde-Ferrell type novel Fermi superfluid. I identified the region where this superfluid state appears in a stable manner, in the non-equilibrium phase diagram in terms of the interaction strength, temperature, as well as the chemical potential difference. I also showed that the bi-stability occurs in this system. In addition, I numerically examined the time evolution of the states appearing this phase diagram, to clarify their stability conditions.

Free Research Field

凝縮系物理学

Academic Significance and Societal Importance of the Research Achievements

非平衡状態にあるフェルミ原子気体において、Fulde-Ferrell状態に類似の超流動状態がスピンインバランスなしで安定に実現しうることが明らかになったことは、様々な分野で進んでいるFulde-Ferrell超流動の実現に向けた研究に大きなインパクトを与える成果であり、学術的意義は大きい。フェルミ原子気体で実現する超流動は、金属超伝導と物理的に同じであることから、本研究の成果は、技術的応用が期待される超伝導研究の発展にも貢献するものとして、社会的意義もあると判断できる。