2023 Fiscal Year Final Research Report
Experimental verification of replica-symmetry-breaking in real spin glasses
| Project/Area Number |
20H01852
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
黒川 修 京都大学, 工学研究科, 准教授 (90303859)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | スピングラス / レプリカ対称性の破れ / 磁化緩和測定 / 磁気ノイズ測定 / スピン偏極STM |
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| Outline of Final Research Achievements |
In this project, we aimed to verify replica symmetry breaking (RSB) in real spin glass (SG) materials by experimentally observing the overlap distribution function of spin arrangements P(q). For this purpose, we conducted research aiming at (I) the indirect observation by magnetic response measurements and (II) the direct observation by spin-polarized STM. The main results of (I) were the observation of the bifurcation of the magnetic susceptibility in the infinite time limit under zero-field cooling and under magnetic field cooling, the determination of the replicon exponent and the chaos exponent, etc., which strongly indicated the RSB in the RKKY Ising SG. As for (II), we prepared the equipment to perform the spin-polarized STM measurements at low temperatures and performed the real-space observations of random spin arrangements in the RKKY Ising SG materials.
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| Free Research Field |
磁性
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| Academic Significance and Societal Importance of the Research Achievements |
レプリカ対称性の破れ(RSB)は、幅広いクラスの「ランダムな秩序」を特徴付ける普遍的な概念として理解され、その重要性から、スピングラスの理論で最初にこの概念を提唱したG. Parisiは、2021年のノーベル物理学賞に輝いている。
一方で、平均場モデルのような非現実的なモデルではなく、現実の物質でRSBが本当に起こっているかどうかついては否定的な意見も多く、全くの未解決問題である。本課題の成果は、実際のスピングラス物質でRSBが起こっていることを強く支持するものであり、ランダムな秩序の理解に大きく貢献するものと言える。
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