Scanning Tunneling Microscopy and Spectroscopy of Vortices in a Superconductor

The core states of individual vortices are imaged with a low temperature scanning tunneling microscope on 2H-NbSe₂. The quasiparticle wavefunctions of different energy are highhghted by tunneling at various bias voltages. The sequence of different energy bound states wavefunction images reveal a continuously evohing star shaped pattern. If the magnetic field is applied at an angle a "comet" shaped structure is observed. These patterns are consistent with previously acquired spectral evolution data, and may result from the anisotropy of the band structure.