2023 Fiscal Year Research-status Report
| Project/Area Number |
23KJ0778
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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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| Keywords | Bosonic transport / Superlattice / Nonreciprocity / Symmetry breaking / Valley / magnon-phonon coupling |
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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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| Causes of Carryover |
We will try to combine the local characterization techniques, such as NV center or X-ray with our results. We thus plan to establish X-ray based facilities in ISSP and synchrotron beamlines(e.g., SACLA or the beamline in Sendai).We will establish the measurement systems which can send current (or microwave), and measure through X-ray.Special sample holder and magnet systems may be designed and established.
We will also buy new consumables，like evaporation targets, substrates, and e-beam lithography resists, and use tralvel fee for presenting the results in international conferences.
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