| 研究実績の概要 |
We sucessfully achieved the depairing Jc in a narrow bridge of FeSe single crystal fabricated by the FIB pick-up technique. Width of the narrow bridge is reduced in sequence from 1.125 μm to 0.388 μm, which is larger and smaller than the value of Pearl length (Λ ~ 0.62 μm), respectively. Jc is directly estimated from the transport current-voltage measurements, which reaches a very large value about one order of magnitude larger than the depinning Jc estimated from the magnetic hysteresis loops (MHLs). Furthermore, the value of Jc is found to be increased more than twice simply by reducing W from 1.125 μm to 0.388 μm, which supports the achievement of depairing Jc. We also measured the Jc under magnetic fields. Jc of the narrow bridge is found to be much stable against magnetic field than that of the bulk sample. The field-insensitive Jc can be understood by the large increase of lower critical field, Hc1, when W is reduced to be comparable to λ
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