| Project/Area Number |
23KJ0778
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| Research Category |
Grant-in-Aid for JSPS Fellows
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| Allocation Type | Multi-year Fund |
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| Section | 国内 |
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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | The University of Tokyo |
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Principal Investigator |
LIAO Liyang 東京大学, 新領域創成科学研究科, 特別研究員(DC1)
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| Project Period (FY) |
2023-04-25 – 2026-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 2025: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2024: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2023: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Bosonic transport / Superlattice / Nonreciprocity / Symmetry breaking / Valley / magnon-phonon coupling |
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| Outline of Research at the Start |
The collective motion of magnetism, the spin waves, can couple to sound waves.In this research, we modulate the coupling between spin wave and sound wave by periodic arrays, who can coherently scatter these waves.We will firstly study the transmission of large samples, and then characterize the spin waves and sound waves directly by optical methods.
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| Outline of Annual Research Achievements |
Bosonic transport is studied via surface acoustic wave transmission. By rotating surface acoustic wave propagation direction on 128-Y LiNbO3 substrate, Y' axis was selected for superlattice study for its suitable symmetry. Superlattice was then fabricated using electron beam lithography, e-beam evaporation and lift-off process.
Ni (20 nm) /Ti (15 nm) was used for the deposition. Square and hexagonal lattices with and without symmetry breaking are fabricated. The surface acoustic wave wavelength was 2000 nm, and the lattice size was selected accordingly, so that the wavevector located at the Brillouin zone corners.The transport efficiency spectrum was measured by the vector network analyzer, and a nonreciprocity controlled by out-of-plane magnetization and lattice symmetry was observed.
Systematic magnetic field manitude,angular,and frequency dependence were performed, clearly established the superlattice origin of the nonreciprocity. The nonreciprocity is controlled by the phononic band structures, as it change sign at the center of the phononic Dirac cone, consistant with the chirality change of the Dirac bands. Such frequency-dependent sign change of nonreciprocity in magnon-phonon coupling is observed for the first time. The results were summarized and published in Physical Review Letters.
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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 achieved the nonreciprocal surface acoustic wave transport controlled by superlattice in this year, as a milestone of this project.
Baesd on this achievement, we can explore more possiblities in the further research.
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| Strategy for Future Research Activity |
We will turn towards to more complicated superlattice structures, to tune the observed nonreciprocity. We will also try to combine the achieved global spectra measurement to local measurements, such as X-ray, NV center. In this way, we may be able to explore more exciting phenomena, such as topological chiral edge modes and Non-Hermitian skin effect.
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