2018 Fiscal Year Annual Research Report
遷移金属カルコゲナイドナノチューブにおける量子輸送現象
| Project/Area Number |
18J14154
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| Research Institution | The University of Tokyo |
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Principal Investigator |
秦 峰 東京大学, 工学系研究科, 特別研究員(DC2)
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| Project Period (FY) |
2018-04-25 – 2020-03-31
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| Keywords | TMD material / nanotube / superconductivity / ionic liquid gating / intercalation / Little-Parks oscillation / diameter-dependent / curvature |
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| Outline of Annual Research Achievements |
We have successfully concluded the relation between superconductivity in WS2 nanotube and its diameter by low temperature transport measurement.
The superconductivity is realized by electrochemical doping via the ionic gating technique. The diameter of the nanotube is evaluated from the periodic oscillating magnetoresistance, known as the Little-Parks effect. On the other hand, the wall thickness is estimated by fitting the temperature dependent upper critical field.
After analyzing experiment data, the critical temperature of superconductivity appears independently to the wall thickness, while it scales linearly as a function of the inverse diameter, that is, the curvature of the nanotube.
This work was highlighted in Nature Nanotechnology 13, 978 (2018).
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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 low temperature quantum transport measurement, we successfully concluded the relation between superconductivity in WS2 nanotube and its diameter. The critical temperature of superconductivity appears independently to the wall thickness, while it scales linearly as a function of the inverse diameter, (the curvature of the nanotube).
This result is a nontrivial result, since people have been believing that that by shrinking the diameter of nanotube the critical temperature should be enhanced. The present results are an important step in understanding the microscopic mechanism of superconductivity in a nanotube, opening up a new way of superconductivity in crystalline nanostructures.
On the other hand, we also start we also started experiments for calibrating optical properties of WS2 nanotube and obtained good results.
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| Strategy for Future Research Activity |
During experiments and previous understanding of nonreciprocal transport phenomena, we realized that the chiral symmetry of rolling up a nanotube and the C3V symmetry of 2H-WS2 unit cell do not match to each other, and thus the symmetry forces the WS2 nanotube to become polar, which can generate an extremely large intrinsic photocurrent without inducing any p-n junction.
We then are interested in such intrinsic second order signal generation in many other different materials and also start to work on other topics. For example, in transport measurement, the symmetry allows that the second harmonic voltage could appear in transvers direction, and one of the microscopically contribution is from both the dispersion of band structure at the Fermi energy and the Berry curvature distribution in the momentum space. Such measurement of second harmonic voltage and also the symmetry engineering will be our recent goal in the near future.
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[Presentation] Superconductivity in a Chiral WS2 Nanotube2018
Author(s)
F. Qin, T. Ideue, W. Shi, M. Yoshida, A. Zak, R. Tenne, T. Kikitsu, D. Inoue, D. Hashizume & Y. Iwasa
Organizer
The 12th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (M2S-2018)
Int'l Joint Research
