  A self-consistent Bogoliubov deGennes theory of the vortex lattice state in a
2D strong type-II superconductor at high magnetic fields reveals a novel
quantum mixed state around the semiclassical Hc2, characterized by a
well-defined Landau--Bloch band structure in the quasi-particle spectrum and
suppressed order-parameter amplitude, which sharply crossover into the
well-known semiclassical (Helfand-Werthamer) results upon decreasing magnetic
field. Application to the 2D superconducting state observed recently on the
surface of the topological insulator Sb2Te3, accounts well for the experimental
data, revealing a strong type-II superconductor, with unusually low carrier
density and very small cyclotron mass, which can be realized only in the strong
coupling superconductor limit.
