Theoretical study on spin-liquid states in frustrated magnets and related problems

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05519
• 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: Tokyo University of Science
• Principal Investigator: Yoshiyuki Fukumoto 東京理科大学, 理工学部物理学科, 准教授 (00318213)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: ハイゼンベルグ模型 / スピン液体 / 球体カゴメ / 量子ダイマー模型 / RVB状態 / 光格子 / ハバード模型 / 擬ギャップ

Outline of Final Research Achievements

We have used the experimental magnetization process and specific heat of the spherical Kagome system {W72V30} to clarify what perturbations are important in this material, and have found that the model Hamiltonian is needed to contain the Dzyaloshinsky-Moriya interaction and a broad distribution of nearest-neighbor exchange interactions, whose magnitudes are about 10% of the average exchange interaction.
We have found a Heisenberg antiferromagnet whose effective low-energy model is the quantum dimer model. We calculated the model parameters in the quantum dimer model as a function of exchange interaction and found that the spin-iquid ground state can be realized.
Chakravarty et al. suggested that the origin of the pseudogap in the high-temperature superconductivity is the d-wave charge density wave. We have found the extended Hubbard model being a microscopic model for Chakravarty's scenario.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

球体カゴメ系{W72V30}の比熱測定で，Resonating Valence Bond(RVB)状態の特徴である，スピンギャップ以下での多数のシングレット状態の存在が示されている。本研究での摂動項の特定を足ががりに，今後，分数励起（スピノン）の観測が期待される。
等方的交換相互作用のみを持つ模型から量子ダイマー模型（ロクサー・キベルソン点含む）を作るレシピが明らかとなり，今後の量子シミュレータでの実現が期待される。
拡張ハバード模型がDDW秩序を持つ可能性が指摘され，今後，数値実験的研究での検証と，DDW秩序のさらなる理解，実験との対比が進むと期待される。