| 研究課題/領域番号 |
20F20020
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| 研究機関 | 京都大学 |
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研究代表者 |
米澤 進吾 京都大学, 理学研究科, 准教授 (30523584)
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| 研究分担者 |
HU YAJIAN 京都大学, 理学研究科, 外国人特別研究員
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| 研究期間 (年度) |
2020-09-25 – 2023-03-31
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| キーワード | Kerr effect / Topological materials / time-reversal-symmetry / charge density wave / Kagome lattice |
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| 研究実績の概要 |
We have successfully constructed an all-fiber magneto-optical Kerr effect setup with sub-microradian resolution, which is able to measure polar Kerr angle at low temperature down to 2 K and under magnetic field up to 11 T. Using this technique, we have studied the charge density wave (CDW) of a Kagome superconductor CsV3Sb5. We have measured the polar Kerr angle of CDW state under magnetic field and at zero field. Under magnetic field, we observed a sharp jump at the CDW transition temperature TCDW, which can be flipped by magnetic field and is almost linear in field. At zero field, we detected finite Kerr angle below TCDW and the sign changes with training field. Our data provide new evidence for the time-reversal symmetry-breaking in the CDW state and its coupling to the external magnetic field, consistent with the loop-current order theory proposed. We are now preparing a manuscript to report these results.
For further improvement of our optics, we are testing a photo-amplifier and spectral filters to amplify the signal.
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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
In the last fiscal year, we devoted much efforts to establish our Kerr-effect setup, and we achieved sufficient stability and sensitivity enough to study various interesting materials. Currently, we are preparing a manuscript about the results of the CDW state of the Kagome material CsV3Sb5. In this material, there are many unconventional properties reported in the superconducting state and the time-reversal symmetry property is important. Our report would have great impact on the research of this compound. We are also measuring the polar Kerr angle in the superconducting state below 2.8 K.
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| 今後の研究の推進方策 |
Beyond low temperature and magnetic field, we will integrate different tuning parameters such as uniaxial strain. The first target is to study the iron-based superconductors Fe(Se,S). These materials show nematic phase transition and two superconducting phases in the temperature-doping phase diagram. The superconducting states are predicted to be time-reversal symmetry-breaking but with different nature. We will measure the doping dependence of polar Kerr angle. By integrating the uniaxial strain device, we can align the nematic domains and study the time-reversal symmetry-breaking across the domain wall.
We are also developing scanning device using bimorph-piezo benders so that we can probe the domains in the sample.
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