Ultrasonic Investigation of Uranium Compounds without Local Inversion Symmetry

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K05525
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Hokkaido University
• Principal Investigator: Yanagisawa Tatsuya 北海道大学, 理学研究院, 准教授 (10456353)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 強相間電子系 / 奇パリティ多極子 / 低温物性 / 磁性 / 超音波

Outline of Final Research Achievements

The elastic response of a uranium compound (UNi4B) exhibiting vortex-like magnetic ordering (magnetic toroidal dipolar ordering), which breaks the spatial inversion symmetry, has been precisely measured by using the ultrasonic phase-comparison method down to very low temperatures and high magnetic fields. We have succeeded in identifying the electric quadrupoles that maintain their degrees of freedom without ordering at the center of a magnetic vortex arrangement in uranium with a honeycomb structure. The response of the quadrupoles depends strongly on the direction of the magnetic field. We discover a new phase V appears at high magnetic fields and low temperatures for H || b. We can conclude that the electric quadrupoles play an important role in the vortex-like magnetic structure of this system, modifying the spin-reorientation process as well.

Free Research Field

超音波電子物性

Academic Significance and Societal Importance of the Research Achievements

磁場下で堅牢な電気四極子自由度を自在に制御できるようになれば、新たな量子メモリや、磁場に対して堅牢な量子デバイスなどへの応用が期待される。今回実証されたのはその基礎となる現象のため，今後はその物理をしっかりと構築することが重要である。また，本研究で採用した強磁場・極低温下における精密超音波測定の手法は様々な化合物に応用可能であり，磁気相図の構築から新奇な量子現象の機構解明に役立てることができる。