| 研究課題/領域番号 |
22K18712
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| 研究機関 | 東京大学 |
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研究代表者 |
Melia Thomas 東京大学, カブリ数物連携宇宙研究機構, 准教授 (30814909)
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| 研究分担者 |
福井 智也 東京工業大学, 科学技術創成研究院, 助教 (40808838)
水上 雄太 東北大学, 理学研究科, 准教授 (80734095)
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| 研究期間 (年度) |
2022-06-30 – 2025-03-31
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| キーワード | Dark Matter / Particle Detector / Single Molecule Magnet |
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| 研究実績の概要 |
The aim of this research was to identify single molecule magnet crystals (SMMs) that had properties that could enable their use as dark matter detectors (be in principle sensitive to a pioneering new low energy threshold). The theory group has calculated that a key parameter of the crystal regarding sensitivity to energy deposit is the magnetic relaxation time, which should be small for higher sensitivity. The chemistry group synthesized three different SMM crystals (Mn6, Mn12, Mn32) with relaxation time in the range 10^-7-10^-12s, and measured the thermal diffusivity. The solid state group worked on the characterization and high resolution heat capacity measurements of these SMMs. From the magnetization and heat capacity measurements, the energy barrier and relaxation time where successfully obtained for Mn12 and Mn32. The theory group used these numbers to estimate the avalanche threshold. In particular, the threshold for Mn32 was found to be potentially as low as 0.1 electronvolt. If this threshold were to be successfully achieved, it would be around an order of magnitude lower than current thresholds in any currently demonstrated quantum sensor. This identifies Mn32 as an ideal pioneering SMM crystal.
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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
The research is progressing rather smoothly because three single molecule magnets (SMMs) were successfully synthesised, two of which had their physical properties (heat capacity) successfully measured at low temperatures. These were the measurements needed as input to the theoretical calculations of sensitivity to dark matter detection. The three SMMs are all identified as very promising candidates for the detector. Two main problems were encountered. First, reproducing reported chemical synthesis in the literature to obtain good quality high yield. Second, the fact that the crystals were small and difficult to synthesize in larger size; this made heat capacity measurements challenging.
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| 今後の研究の推進方策 |
We now plan to assess the stability of the single molecule magnet (SMM) crystals identified in this work as particle detectors, and to fully characterise properties of their avalanches. The solid state group will study avalanches triggered by heat or magnetic field by means of magnetization measurements, as detected through e.g. a Hall sensor glued to the SMM. There will be feedback to follow-up chemical synthesis (chemical fine-tuning of crystal composition by modifying chemical structure of ligands, size of crystal using seeded crystallization). We also plan to demonstrate the sensitivity of a crystal to a small energy deposit.
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| 次年度使用額が生じた理由 |
The amount will be used for travel purposes, to disseminate the obtained results at research conferences and to collaborate with researchers in the US collaboration to further the development of the single molecule magnet crystal detector. These meetings are in accordance with the research plan, but were not able to be arranged within the fiscal year, resulting in unspent amounts.
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| 備考 |
This research established an international collaboration with researchers in the US
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