Regensburg 1998 – wissenschaftliches Programm

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PV: Plenarvorträge

PV XV

PV XV: Plenarvortrag

Donnerstag, 26. März 1998, 08:30–09:15, H1

Dynamics of Superconducting Vortices by Electron Waves — •Akira Tonomura — Advanced Research Laboratory, Hitachi Ltd., Hatoyama, Saitama 350-0395, Japan

Dynamic behaviour of tiny vortices holds the key to practical applications of superconductors as conducting wires, since vortices begin to move by a Lorentz force due to a current thus breaking down the superconducting state unless vortices are pinned down by defects. In order to elucidate the microscopic mechanism of the vortex pinning, we developed a method to dynamically observe both vortices and defects unsing a 350 kV field-emission electron microscope. With this Lorentz microscopy, an electron wave is incident onto a superconducting thin film and the phase shifts due to vortices are detected as spots by defocusing the electron microscopic image [1]. We observed how vortices moced when a force was exerted on them, and found various kinds of vortex flows when there existed artificial pinning centers [2,3].

[1] A. Tonomura: No-dqElectron HolographyNo-dq(Springer Verlag: Heidelberg, 1993)

[2] T. Matsuda et al.: Science 271 (1996) 1393-1395

[3] K. Harada et al.: Science 274 (1996) 1167-1169