Exploration of quantum transport induced by emergent magnetic field in real and momentum space

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20348
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0202:Condensed matter physics, plasma science, nuclear engineering, earth resources engineering, energy engineering, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Yamada Rinsuke 東京大学, 大学院工学系研究科(工学部), 助教 (80962133)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: トポロジカル物質 / 強相関電子系 / 熱電効果 / 量子輸送

Outline of Final Research Achievements

In this study, we aim to search for novel quantum phenomena due to the interplay of spin structure in real space and electronic structure in momentum space. Specifically, we focused on RAlSi (R = rare earth), a magnetic Weyl semimetal with broken spatial inversion symmetry. Here, we used the thermoelectric effect, which is known to be a sensitive probe of the electronic state near the Fermi surface. The Nernst effect in NdAlSi increases toward lower temperatures and reaches a maximum at slightly higher temperatures than the magnetic transition temperature. Combining the semiclassical model analysis with first-principles calculations of the band structure, it is found that the enhancement near the magnetic transition temperature is due to an anomaly in the scattering time associated with the Fermi surface nesting.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

従来の熱電効果は物質のキャリア数が少なくなるほど増大するため、候補物質の探索領域が希薄キャリア半導体を中心としたものに限られることが多かった。本研究では、磁気的な周期構造を有する物質の磁気転移温度付近で、散乱時間の揺らぎによって熱電効果が増大する可能性を明らかにした。この効果は、キャリア数の多い金属的な試料でも発現することから、より幅広い物質において発現すると考えられ、熱電効果の探索領域が拡大することが期待される。今後は、磁気的な周期構造にとどまらず、電荷の周期構造（電荷密度波）に起因した熱電効果の探索が興味深い研究方針と考えられる。