Experimental study on the dynamics of topological defects in solid Helium

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K03839
• 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: Ashikaga University
• Principal Investigator: Takahashi Daisuke 足利大学, 工学部, 教授 (80415215)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 量子固体 / 転位

Outline of Final Research Achievements

Solid helium-4 contains only helium-3 isotopes as impurities, it serves as an ideal solid for investigating the dynamic properties of topological defects within the solid. This study examined the dynamic properties of dislocations, which is a typical topological defect in the solid, that contribute to the temperature dependence of the shear modulus, a classical physical quantity of solid helium-4. By measuring the elastic changes in solid helium-4 confined within a double pendulum that shows sensitive responses to elastic modulus variations, we verified observed changes in elastic modulus that are difficult to explain using existing dislocation theories. These results suggest the presence of novel dynamic properties in dislocation motion.

Free Research Field

低温物理学

Academic Significance and Societal Importance of the Research Achievements

トポロジカル欠陥としての転位の動的性質は結晶・非結晶体の多くで相転移を含めマクロな物性変化の核心的駆動体となる可能性が示唆されているが，他の系においては転位以外の要因を適切に取り除くことが困難である。一方，固体ヘリウム4は素性の知れた同位体としての不純物のみを考慮することで，転位の動的性質を議論することが可能となる。本研究で明らかになった固体ヘリウム4の新奇な転位ダイナミクス存在の可能性は既存の転位論の深化へ大きく寄与すると考えられる。