2021 Fiscal Year Annual Research Report
Experimental study of topological phases in strongly correlated system
| Project/Area Number |
20F20315
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| Research Institution | The University of Tokyo |
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Principal Investigator |
中辻 知 東京大学, 大学院理学系研究科(理学部), 教授 (70362431)
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| Co-Investigator(Kenkyū-buntansha) |
FENG ZILI 東京大学, 理学(系)研究科(研究院), 外国人特別研究員
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| Project Period (FY) |
2020-11-13 – 2023-03-31
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| Keywords | Nodal line / Anomalous Nernst Effect |
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| Outline of Annual Research Achievements |
Fe3Ga is a ferromagnetic metal with a Curie temperature of 720 K and exhibits a giant anomalous Nernst effect (ANE) about 5.8 μV/K at room temperature. Owning to the high symmetric crystal structure, the nodal web band structure is proposed as the origin of the large ANE in Fe3Ga. However, the nodal web is 12 meV below the Fermi level of Fe3Ga. Thus, optimizing the composition to tune the Fermi level is an important issue for the ANE sample. The crystal structure of Fe3Ga is reported stable against the slight change in chemical composition, as a result, the symmetry-protected nodal web should be robust, guaranteeing a large ANE in a relative wide composition window. We focus on the Fe-doping effect on the transport properties for polycrystalline FexGa4-x (2.96 < x < 3.15).
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
We systematically study the composition dependence of properties of the polycrystalline cubic ferromagnet Fe3Ga system and find a large ANE 5.4 μV/K in Fe3.09Ga0.91 at room temperature. This value hits a record high among any reports for polycrystalline samples. Meanwhile, the large ANE is even very robust against the composition deviation, keeping a higher value than 5.1 μV/K for a wide range of composition. Combining the experimental result and DFT calculation, we demonstrate how the nodal web shifts to the Fermi level by increasing Fe content without destroying the nodal web band structure.
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| Strategy for Future Research Activity |
Our results demonstrate a new strategy to enhance the ANE in ferromagnetic compounds. Moreover, the excellent performance, low cost, and nontoxicity make the polycrystalline Fe3Ga system a most promising candidate for energy-harvesting devices and heat-current sensors for real-life applications. Therefore, next we plan to design a thermoelectric module using Fe3.09Ga0.91 polycrystal. This thermoelectric module is set up by connecting several Fe3.09Ga0.91 rectangular bar which can generate a sizeable electric voltage. We will test and optimize the output power above room temperature. This would be very important to promote the real application using ANE effect.
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