| 研究課題/領域番号 |
23KJ2136
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| 研究種目 |
特別研究員奨励費
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| 配分区分 | 基金 |
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| 応募区分 | 国内 |
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| 審査区分 |
小区分13030:磁性、超伝導および強相関系関連
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| 研究機関 | 沖縄科学技術大学院大学 |
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研究代表者 |
Bao Jiahui 沖縄科学技術大学院大学, 科学技術研究科, 特別研究員(DC1)
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| 研究期間 (年度) |
2023-04-25 – 2026-03-31
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| 研究課題ステータス |
交付 (2023年度)
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| 配分額 *注記 |
2,700千円 (直接経費: 2,700千円)
2025年度: 900千円 (直接経費: 900千円)
2024年度: 900千円 (直接経費: 900千円)
2023年度: 900千円 (直接経費: 900千円)
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| キーワード | magnon excitations / cuprate superconductor / DMRG / tensor networks / Hubbard model / spin wave theory |
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| 研究開始時の研究の概要 |
The exotic exicitations of cuprate compounds observed in neutron scattering experiements lead to possible connections with novel quantum spin liquids and the nature of their superconductivity. In order to exoplore the nature of the exicitations, in this project we use density matrix renormalization group (DMRG) and matrix product state based time evolution methods to simulate the dynamical properties of the effective model of the cuprates. Combining analytical calculations of spin wave theory and existing experimental data, we aim to clarify whether spinons exist beyond the magnon picture.
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| 研究実績の概要 |
As originally proposed, this project aims to understand the nature of unconventional excitations in cuprates. This year, I have finished the calculations based on matrix product states (MPS) to compare the experiment of La2CuO4 with the predictions of a spin model derived from a one-band Hubbard model. The spin model is found to give an excellent account of the dispersion of magnetic excitations in La2CuO4 throughout the Brillouin zone, and also provides a good account of their intensity and lineshape, except approaching the point q = (π, 0), where the experiment reveals a continuum of excitations at high energy. I further discuss the application of these results to CaCuO2 and Sr2IrO4, and identify an empirical scaling relation that can be used to extract a value of t/U from the experiment. These results suggest that a one-band Hubbard model captures most, but not yet all, of the properties of undoped cuprate antiferromagnets.
I have written these results as a journal article, and the manuscript is in its final stage. I will submit it to an international journal in the near future. I have also presented this work as both a contributed talk and a poster presentation at conferences and workshops.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
In my proposal, the goal of this project is to understand the nature of the anomalous high-energy continuum in the excitation spectrum. As the calculations were carried out, the continuum is not fully reproduced by the one-band Hubbard model. However, I found the physics of magnons in this context to be interesting and useful for experiments, including the comparison with spin wave theory. Therefore, I decided to publish the results I have now.
Regarding the information spreading, I also did some calculations about out-of-time-order correlators (OTOC) in a one-dimensional model. Nonetheless, the computational cost is much higher than that of the dynamical structure factor. Therefore, studying it in a two-dimensional model with complicated ring exchange interactions is still challenging until the methods are improved.
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| 今後の研究の推進方策 |
Having seen that the one-band Hubbard model is not able to fully capture the physics of the high-energy continuum, I plan to study whether including additional terms can help to reproduce it. These may include the Dzyaloshinskii-Moriya interaction or hopping beyond nearest neighbors.
Moreover, I have also been working on spin-orbit coupling and quantum spin nematics, which are both closely related to the compound Sr2IrO4 studied in the current project.
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