Itinerant and localized 5d multipoles in the pyrochlore oxides

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01169
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Tokyo
• Principal Investigator: Hiroi Zenji 東京大学, 物性研究所, 教授 (30192719)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: スピン軌道結合金属

Outline of Final Research Achievements

Cd2Re2O7 is a candidate for the spin-orbit-coupled metal (SOCM). SOCM is a metallic system characterized by a centrosymmetric crystal structure and conduction electrons with strong spin-orbit interactions. It has a specific Fermi liquid instability that causes spontaneous inversion symmetry breaking leading to unusual odd-parity multipolar orders. We prepared single crystals with the (001) surface and applied anisotropic stress to control the tetragonal domains. Resistivity measurements using single-domain crystals revealed anisotropy in resistivity as large as 25%, which turned over at Ts2 = 120 K. The origin of the large anisotropy must be spin-dependent scattering in the spin-split Fermi surfaces of the odd parity multipolar orders, which carry important information on the characteristics of the SOCM.

Free Research Field

固体物性化学

Academic Significance and Societal Importance of the Research Achievements

金属状態を特徴付けるフェルミ面はさまざまなフェルミ液体不安定性を有し、電子系の相転移を誘起する。例えば、電子格子相互作用があれば、フェルミ面に超伝導ギャップが開いて超伝導状態となり、磁気的な不安定性は磁気秩序をもたらす。スピン軌道結合金属ではスピン軌道相互作用に基づく新規なフェルミ液体不安定性が奇パリティ多極子秩序を誘起すると予想されているが、その実験的検証は不十分である。本研究はCd2Re2O7がモデル物質であることを示し、スピン軌道結合金属が物性物理学の教科書に追記されるべき新たな概念であることを示した。