Seminar: "Observation of Superconducting Vortices by Transmission Electron Microscopy" Ken Harada, Hitachi, Ltd.

Seminar: “Observation of Superconducting Vortices by Transmission Electron Microscopy”

Speaker: Dr. Ken Harada, Central Research Laboratory, Hitachi, Ltd.

Date/Time: Tue 28^th May / 16:00-17:00

Location: Seminar Room C210, Level C, Center Building

Observation of Vortices in Superconductors by Transmission Electron Microscopy

Ken Harada

Central Research Laboratory, Hitachi Ltd.

The dynamic behavior of quantized magnetic-flux lines (vortices) is very important for practical use of superconductors. In order to unveil the properties, many kinds of techniques to observe individual vortices have been developed after the discovery of the high-T_c superconductors. However, the observation of their dynamics still remains difficult even now, because vortex is small in size (a few hundred nm in diameter) and has small magnetic flux (2.07 × 10^-15 Wb). Lorentz microscopy using a transmission electron microscope (TEM) is one of the powerful tools to observe vortex dynamics in real time. The first observation of the dynamics of individual vortices inside niobium (Nb) thin films was succeeded in 1992. We have continued improving our microscopy techniques and have developed application techniques from the first success.

In the seminar, I would like to introduce the microscopy for observing vortices with some technical aspects, for example cooling system and magnetic field application system mounted inside the TEM.  I will also show some application results are also introduced, for example pair-annihilation of anti-parallel vortices in Nb, structure change of vortices trapped at columnar defect in Bi₂Sr₂CaCu₂O_8+d (Bi-2212), chain structure of vortices in Bi-2212 and YBa₂Cu₃O_7-d (Y-123), etc. The seminar talk will be a review and introduction to the research work on vortices in superconductors by using TEM.

Host: Professor Nic Shannon / Contact: shiho.saito@oist.jp