Critical phenomena of superfluid quantum transition in a one-dimensional Helium system

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03535
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Electro-Communications
• Principal Investigator: Taniguchi Junko 電気通信大学, 大学院情報理工学研究科, 准教授 (70377018)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: １次元量子系 / 超流動 / 朝永－ラッティンジャー液体

Outline of Final Research Achievements

Helium 4 confined in a nano-channel is an ideal system to study the effect of the strong quantum fluctuation specific to a one-dimensional (1D) system. We have performed the measurements of the vapor pressure and heat capacity for 4He adsorbed on a 2.8-nm channel of mesoporous silica, and evaluated the phase diagram of 4He film. With increasing areal density, the amount of excited fluid decreases and tends to zero just below the “quantum critical point (areal density) of superfluidity” (n_c). Above n_c, liquid phase 4He appears and shows superfluidity at low temperature. For 4He confined in 2.8-nm channel under pressure, we are proceeding with the simultaneous measurements of an ultrasound and a torsional oscillator. Under 1.3 MPa, the ultrasound attenuation peak temperature T_Pus is located at around 1 K, which is more than 0.4 K higher than the dissipation peak T_Pto by torsional oscillator. To investigate the origin of the difference between T_Pus and T_Pto is a future issue.

Free Research Field

低温物理

Academic Significance and Societal Importance of the Research Achievements

従来，量子臨界現象は電子（フェルミ）系における超伝導‐絶縁体転移が主な研究対象として研究されてきた．一方，本研究は，１次元ヘリウム系という，電子系とは量子統計性も相互作用の性質も大きく異なる系を対象として，その臨界現象の一端を明らかにしてきた．このように統計性・相互作用が大きく異なる系での研究成果は，低（１）次元量子系の研究の多様性・フロンティアを広げることに資する．