ABSENCE OF DIPOLE TRANSITIONS IN VORTICES OF TYPE-II SUPERCONDUCTORS

The response of a single vortex to a time-dependent field is examined microscopically and an equation of motion for vortex motion at nonzero frequencies is derived. Of interest are frequencies near DELTA-2/E(F), where DELTA is the bulk energy gap and E(F) is the Fermi energy. The low-temperature, clean, extreme-type-II limit and maintenance of equilibrium with the lattice are assumed. A simplification occurs for large planar mass anisotropy. Thus the results may be pertinent to materials such as NbSe2 and high-temperature superconductors. The expected dipole transition between core states is hidden because of the self-consistent nature of the vortex potential. Instead the vortex itself moves and has a resonance at the frequency of the transition.