Imaging of the Spatial Structure of Inhomogeneous Energy-Gap States in Nonequilibrium Superconductors

Using Low Temperature Scanning Electron Microscopy (LTSEM) the spatial structure of inhomogeneous energy gap states in nonequilibrium PbIn-alloy films has been studied under injection of quasiparticles both at and well above the gap sum voltage. By LTSEM for the first time the spatial homogeneity of the quasiparticle injection and the spatial distribution of the energy gap of the perturbed film have been imaged directly with a spatial resolution of a few µm. In this way the nucleation and the spatial development of the inhomogeneous energy gap state with increasing quasiparticle injection and the characteristic length scales of the inhomogeneous state can be observed directly.