T. Nishio et al., QUASI-PARTICLE BAND-STRUCTURE AND GAPLESS SUPERCONDUCTIVITY IN THE VORTEX-LATTICE STATE, Journal of the Physical Society of Japan, 66(4), 1997, pp. 953-956
The quasi-particle spectrum for s-wave superconductors in the Vortex-l
attice state remains gapless in magnetic fields much below the upper c
ritical field H-c2 where the cyclotron frequency is smaller than the a
mplitude of the pair potential. This is shown through self-consistent
solutions of the Bogoliubov-de Gennes equations for the attractive Hub
bard model on the square lattice. It has not been predicted in earlier
theoretical works based on a continuous model because it is due to th
e dispersion of Landau subbands in the lattice model.