Imaging of vortices in superconductors by electron beam scanning

Abstract

Abrikosov vortices trapped in a superconducting tunnel junction and oriented perpendicular to the barrier plane were imaged by electron beam scanning at 1.6 K. We have used NbAlOxNb junctions. As an important feature, the top Nb electrode was covered with a SiO2 film of 300 nm thickness, absorbing most of the 5 keV beam energy. The signal generating the image is explained by a model, assuming that the beam-induced electronic excitations in the SiO2 overlay film are trapped in the local magnetic field protruding from a vortex, resulting in an increased recombination rate. In addition to providing a novel approach to the imaging of the vortices in superconductors, our results are important for understanding quasiparticle losses in tunnel junction detectors.

Scanning probe microscopy of high-temperature superconductors

“…The beam can be composed of electrons, ions or photons. A recent example is the work of Huebener's group, where a focused beam of electrons changes the voltage across a superconducting tunnel junction biased at constant current [91]. The electrodes of this junction are made from Nb thin films.…”