A Study on Novel Spin Liquid Phases Emerging on the Pyrochlore Lattice

2018 Fiscal Year Final Research Report

• Project/Area Number: 26400399
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Mathematical physics/Fundamental condensed matter physics
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: Otsuka Hiromi 首都大学東京, 理学研究科, 助教 (10254145)
• Research Collaborator: OKABE Yutaka ; KADOWAKI Hiroaki ; NOMURA Kiyohide
• Project Period (FY): 2014-04-01 – 2019-03-31
• Keywords: スピンアイス / モンテカルロ法 / 交流磁気応答 / 希釈効果

Outline of Final Research Achievements

In this research project, we have investigated the so-called spin ice representing the spin degrees of freedom of rare-earth ions in the compounds such as R2Ti2O7 (R=Dy,Ho); in particular we have focused on novel phenomena stemming from the macroscopic degeneracy in their ground states. We proposed the scaling form for the ac magnetic susceptibility observed in the so-called Kagome ice, which will be compared with the experimental results in future.
Also, we proposed a new type of Monte Carlo algorithm which is free of the critical slowing down problem in the ordinary single-spin flip algorithms. Further, we investigated the diluted spin ice models by analytical and numerical methods, and then clarified that the Bethe approximation works well also for the diluted spin ice. The research for quantum spin systems on the pyrochlore lattice is currently under progress.

Free Research Field

物性基礎論・統計力学

Academic Significance and Societal Importance of the Research Achievements

学術的意義について：AC磁気応答の研究ではAC帯磁率に対するスケーリング則を提案したが、それは二次元スピン液体相が普遍的に示すもので広範な系を対象とした関係式である為、スピンアイスでの実験的検証も含め注目されている。スピンアイスに対するモンテカルロ法の研究では臨界減速の起きないクラスターアルゴリズムを提案しており、同系の数値研究が大幅に進むと期待される。スピンアイスに対する希釈効果の研究ではベーテ近似の一種であるHusimi-Cactus近似を用いてフラストレーション系を定量的に取り扱えることを確認できた。このことは今後の研究に対して重要な意義を持つ。