2021 Fiscal Year Annual Research Report
Probing and controlling topological superconductivity under vector magnetic field and pressure
| Project/Area Number |
20F20020
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| Research Institution | Kyoto University |
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Principal Investigator |
米澤 進吾 京都大学, 理学研究科, 准教授 (30523584)
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| Co-Investigator(Kenkyū-buntansha) |
HU YAJIAN 京都大学, 理学研究科, 外国人特別研究員
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| Project Period (FY) |
2020-09-25 – 2023-03-31
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| Keywords | Kerr effect / Topological materials / time-reversal-symmetry / charge density wave / Kagome lattice |
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| Outline of Annual Research Achievements |
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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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
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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| Strategy for Future Research Activity |
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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[Presentation] Polar Kerr effect study on the charge ordered state in Kagome superconductor CsV3Sb52022
Author(s)
Yajian Hu, S. Yamane, G. Mattoni, Y. Li, Y. Yao, Z. Wang, J. Wang, C. Farhang, J. Xia, S. Yonezawa, Y. Maeno
Organizer
新学術領域研究「量子液晶の物性科学」領域研究会
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[Presentation] Polar Kerr effect study on the time-reversal symmetry-breaking charge ordered state in Kagome superconductor CsV3Sb52022
Author(s)
Yajian Hu, 山根聡一郎, Giordano Mattoni, 矢田歌菜絵, Yongkai Li, Yugui Yao, Zhiwei Wang, Jingyuan Wang, Camron Farhang, Jing Xia, 米澤進吾, 前野悦輝
Organizer
日本物理学会第77回年次大会
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[Presentation] 磁気Kerr効果測定による超伝導体の時間反転対称性の破れの探索2022
Author(s)
山根聡一郎, Yajian Hu, 小畑慶人, Giordano Mattoni, Yongkai Li, Yugui Yao, Zhiwei Wang, Jingyuan Wang, Camron Farhang, Jin Xia, 米澤進吾, 前野悦輝
Organizer
日本物理学会第77回年次大会
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[Presentation] ナノラジアン分解能を持つKerr効果測定の確立と時間反転対称性の破れの模索2022
Author(s)
Soichiro Yamane, Y. Hu, G. Mattoni, Y. Li, Y. Yao, Z. Wang, J. Wang, C. Farhang, J. Xia, S. Yonezawa, Y. Maeno
Organizer
応用物理学会 量子ビームによる表面界面の光機能探究研究会
Invited
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