| 研究課題/領域番号 |
26400339
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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 |
JAUBERT LUDOVIC 沖縄科学技術大学院大学, Theory of Quantum Matter Unit, 研究員 (10727209)
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| 研究分担者 |
宇田川 将文 学習院大学, 理学部, 准教授 (80431790)
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| 研究期間 (年度) |
2014-04-01 – 2017-03-31
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| キーワード | frustrated magnetism / spin ice / magneto-electric / out-of-equilibrium |
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| 研究実績の概要 |
During FY2015 we have concluded the first main project of our Kakenhi, which gave rise to a 27-page long manuscript available on arXiv (1603.02872) in accordance with our open-access policy. We studied how further neighbor spin-exchange, possibly induced by RKKY interactions in itinerant magnets, enhances the range of properties in spin-ice materials. Motivated by experiments on Pr2Ir2O7, we especially considered the non-equilibrium outcome of a field quench, allowing for an interesting connection between Condensed Matter and non-equilibrium Statistical Physics, as confirmed by oral presentations in these two communities: the International Conference on Magnetism (Barcelona), the JPS autumn meeting (Osaka) and an invited talk at the workshop "New Frontiers in Non-equilibrium Physics" (Kyoto).
We have also started to study 1) magneto-electric effects in pyrochlores with Heisenberg spins and 2) quantum effects in breathing pyrochlores, with the help of one postdoc (Karim Essafi, OIST) and two summer interns for their 1st-year Master theses: Etienne Jussiau (ENS Lyon) and Maxime Garnier (ENS Cachan). The latter project was not originally planned in our proposal but is very timely and complements our goal to learn how to engineer spin-ice properties, here via lattice distortion.
To conclude, we had the privilege to invite Prof. Chalker (Oxford) for his first visit to Japan, with whom we had numerous discussions and who gave a mini-series of lectures at Tokyo University and a seminar at OIST.
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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
As we started our project in FY2014, we got the opportunity to edit the first book on Spin Ice. The initial stage of this book edition slightly delayed our project, but we believe that we have now mostly made up for this delay during FY2015.
We were particularly pleased by the fact that the outcomes of our first work (arXiv:1603.02872) were noticeably more diverse than originally anticipated, bringing to light new phases of matter at equilibrium and new relaxation mechanisms out of equilibrium.
Furthermore we could initiate two new promising projects (magneto-electric effects with Heisenberg spins and lattice distortion in quantum breathing pyrochlores) which will be continued during FY2016.
Also it was our plan to take advantage of our Kakenhi to strengthen our scientific network. This was done 1) during several conferences where we advertised our Kakenhi project, in Japan and abroad, and in particular during an invited talk at the Yukawa Institute for Theoretical Physics (Kyoto University) and 2) by inviting Prof. John Chalker, world-leading expert in Condensed Matter, for his first visit to Japan. We especially hope that the mini-series of lectures he gave at the University of Tokyo has been of benefit to the physics community.
Last but not least, we have now received a draft of all chapters from our co-authors for the book on Spin Ice.
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| 今後の研究の推進方策 |
During FY2016, we will pursue our work on magneto-electric effects to study the diversity of phases they beget in a frustrated environment. This is a very technical problem if one includes long-range dipolar interactions and should pave the way to multiferroic properties of pyrochlore materials. In collaboration with Dr Karim Essafi (OIST), we are also aiming at putting a benchmark on the ground states of breathing pyrochlores for spin S=1/2 and 3/2, directly motivated by Ba3Yb2Zn5O11 and LiInCr4O8 compounds, using lattice distortion to explore what lies beyond traditional spin-ice physics.
Another project we have already discussed during our visits between Tokyo and Okinawa is the inclusion of itinerant electrons onto recently discovered chiral kagome spin liquids [1]. Taking advantage of our mutual expertise in Monte Carlo simulations and Kubo formula in conducting problems, the inherent chirality of the localized spins is a promising ingredient to induce anomalous Hall effects while preserving a high degree of magnetic disorder in these systems. Furthermore, our initial results on out-of-equilibrium relaxation in pyrochlores (arXiv:1603.02872) call for a more thorough investigation in other frustrated geometries which will be carried out in collaboration with Mr Mizoguchi (University of Tokyo).
Finally, if time allows, we want to pursue our initial plan to investigate thermal Hall effects in pyrochlores, motivated by recent experiments on Tb2Ti2O7 [2].
[1] K. Essafi et al Nature Commin. 7:10297 (2016) [2] Hirschberger et al. Science, 348, pp 106 (2015)
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| 次年度使用額が生じた理由 |
As we will be finishing our joint project, and the edition of the book, we are expecting more frequent visits from M. Udagawa to OIST and from L. Jaubert to the University of Gakushuin. Moreover since our work has now led to collaborations with Mr Mizoguchi (Univ. Tokyo) and Dr Essafi (OIST), traveling costs can be expected to increase during FY2016. This is one of the reasons why we have saved part of the budget for the final year of our Kakenhi.
Additionally, L. Jaubert might need to replace his present laptop during FY2016.
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| 次年度使用額の使用計画 |
Our funds will continue to be used to finance the collaboration between M. Udagawa and L. Jaubert. Our Kakenhi is especially important to allow for regular visits between the University of Gakushuin and OIST, but also to pay for conferences, publication fees and possibly to invite experts at Gakushuin University and at OIST.
During FY2016, our budget might also cover the travel expenses of our recent collaborators in the project: Mr Mizoguchi (Univ. Tokyo) and Dr Essafi (OIST).
Finally, L. Jaubert might need to buy a new laptop during the coming year.
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