Dynamics and nonlinear response of strong correlated Bose superfluid

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05568
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Mathematical physics/Fundamental condensed matter physics
• Research Institution: Tokyo Medical and Dental University
• Principal Investigator: Hieda Mitsunori 東京医科歯科大学, 教養部, 教授 (30372527)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 超流動 / 非線形効果 / KT転移 / ボーズ流体 / ヘリウム4

Outline of Final Research Achievements

We studied superfluid response of strongly correlated helium-4 in various dimensions by a quartz crystal microbalance (QCM) with the wide frequency range of 20 - 500 MHz. Main results we obtained are as follows. (1) We succeeded to observe superfluid response of two-dimensional helium-4 at microwave frequencies beyond 300 MHz. This observation is the first successful case in the world. (2) We experimentally revealed a frequency dependence of the critical velocity of the nonlinear effect of the two-dimensional superfluid under rotation at high frequencies. (3) We measured shear acoustic impedance of bulk helium-4 at various high frequencies. The experimental data of the frequency dependence are phenomenologically described by the effective viscosity model of elementary particles, phonon and roton.

Free Research Field

低温物理

Academic Significance and Societal Importance of the Research Achievements

スーパークリーンなヘリウム量子流体は超流動の機械的応答研究ができるオンリーワン系であり強相関ボーズ流体に関する基礎研究の理想的なモデル系である。本研究成果により超流動ダイナミクスの断片が明らかにされ、また高周波を使った研究の新たな可能性を示した。これらの結果は強相関ボーズ系における普遍性を捉えたものと考えられ、他の強相関ボーズ系（超伝導体、磁性体、電子、冷却原子気体、結晶、液晶、クオーク）の研究においても大きな前進になるものと考える。