Observation of Vortices in Superconductors

Abstract

Electron holography was originally proposed as a means of improving the resolution of the transmission electron microscope (TEM). And within the last decade dramatic improvements in coherent field-emission electron sources, coupled with TEM instrumentation, have allowed the promise of holography to come to fruition. These improvements in TEM resolution notwithstanding, it has been the application of holography techniques and coherent-beam imaging to the investigation of magnetic and electric fields that has sparked the interest of materials scientists. Electron holography is a unique tool for probing phenomena in the microscopic world because all the information about the object is contained in the hologram (both the electron wave's amplitude and phase), whereas conventional microscopy records only the intensity. It is in this sensitivity to the phase that materials scientists can observe the true potential of electron holography.Electromagnetic phenomena in a wide range of materials systems have been observed via electron holography; domain structures in magnetic particles and electric fields in p-n junctions are just two examples. Furthermore, fundamental physical properties, such as the existence of the vector potential predicted by Aharonov-Bohm (the AB effect), have been conclusively demonstrated by electron holography. For more information, interested readers are referred to several reviews of electron holography.