Electrostatics of Vortices in Type II Superconductors
  In a type II superconductor the gap variation in the core of a vortex line induces a local charge modulation. Accounting for metallic screening, we determine the line charge of individual vortices and calculate the electric field distribution in the half space above a field penetrated superconductor. The resulting field is that of an atomic size dipole ${\bf d} \sim e a_{{\rm B}} {\bf {\hat z}}$, $a_{{\rm B}} = \hbar^2/m e^2$ is the Bohr radius, acting on a force microscope in the pico to femto Newton range. 
Gianni Blatter, Mikhail Feigel'man, Vadim Geshkenbein, Anatoli Larkin,   and Anne van Otterlo