Strongly correlated electronic phenomena induced by multipolar degrees of freedom in non-Kramers systems(Fostering Joint International Research)

2018 Fiscal Year Final Research Report

• Project/Area Number: 15KK0169
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Hiroshima University
• Principal Investigator: Onimaru Takahiro 広島大学, 先端物質科学研究科, 教授 (50444708)
• Research Collaborator: Gegenwart Philipp アウグスブルグ大学, Institute for Physics, Professor ; Mignot Jean-Michel レオン・ブリルアン研究所, CEA-CNRS Saclay, Researcher
• Project Period (FY): 2016 – 2018
• Keywords: Quadrupole / Superconductivity / Neutron scattering / Thermal expansion / Magnetostriction

Outline of Final Research Achievements

We have studied low-temperature transport and magnetic properties of intermetallic cubic systems PrT2Zn20 (T=Ir, Rh) with active quadrupoles of 4f2 electrons. Using high-quality single crystals prepared by myself, we performed neutron scattering experiments at LLB, France, and thermal expansion and magnetostriction measurements at University of Augsburg, Germany. We succeeded in determination of the order parameter of the quadrupole order and revealed a divergent behavior of the thermal expansion coefficient. The results suggest strong interplay between the quadrupolar degrees of freedom and the conduction electrons.

Free Research Field

磁性、低温物性、超伝導

Academic Significance and Societal Importance of the Research Achievements

銅酸化物やセリウム化合物などの強相関電子系では，主に磁気モーメント（スピン）が磁性や超伝導を担っている。本研究では，磁気モーメントよりも高次のテンソル量である電気四極子（異方的な電荷分布）に着目し，四極子と伝導電子の相関によって生じる電気的・磁気的性質について調べた。四極子の秩序状態を微視的プローブである中性子散乱により同定し，また熱膨張係数が秩序状態においても発散的に振る舞うことを初めて明らかにした。これらの結果より，四極子は磁気モーメントと同様に多彩な物性を担っており，強相関電子系における重要な自由度であることが分かった。