| 研究実績の概要 |
We have successfully fabricated a series of a c-axis lamella by the FIB pick-up technique in high-quality FeSe and FeTe0.6Se0.4 single crystals. With this lamella, we can put contacts along the c-axis, to directly measure the out-of-plane transport properties.The deparing current density (Jc) for FeSe was obtained for both along c axis and in the ab plane. The anisototropy of depairing Jc was also obtained, and find to be consistent to the anisotropy estimetaed from the upper critical field (Hc2). Besides, the resistivity, current-voltage curve, critical current density, upper critical fields, and magnetoresistance with current along c axis were studied.
We have successfully intercalated H+ into the FeSe single crystals by gating technique. The superconudcting transition temperature Tc was found to be enhanced over 40 K. More interesting, a discrete superconducting phase diagram with different Tc steps were observed, which is quite distinct from the dome-shaped phase diagram as established in most superconductors.
We have set up a new low temperature measurmental system with 9 T magnetic field, including a sample probe with rotator. With such system, we succeeded in the transport measurement of the FIB microfabricated samples and the EDL devices under magnetic field with different angles.
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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
For crystal fabrication, we have already made thin flakes in Fe(Te,Se) single crystals both along c axis and ab plane. Some transport properties were studied based on these flakes.
For the measuremental system, we have finished setting up the system of 9 T magnetic filed with rotating probe. Some measurements under field with angle reslution have already been performed.
For the gating, we have already successfully intercated the H+ into the FeSe single crystal, and enhanced the Tc over 40 K.
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| 今後の研究の推進方策 |
Based on the systematic measurements above, I will conculde the relation of the band structure and the superconducting gap structure with the Tc increase in the ion-gated Fe(TeSe) compounds, and find out the key factors directly related to the high Tc in FeCh system. Then, I will try to include more research into the micro-structure fabricated EDL devices, such as the nematic state from the in-plan anisotropy, which will provide a new clue to study the relation of nematic order with superconductivity. I will also try to explore the current technique into other systems such as the iron arsenide and topological superconductors. Finally, I will summarize the project and prepare for the application of next project.
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