Quasi-particle spectrum around a single vortex in s-wave superconductors

Making use of the Bogoliubov-de Gennes equation, we study the quasi-particle spectrum and the vortex core structure of a single vortex in quasi 2D s-wave superconductors for small $p_F\xi_0$, where $p_F$ is the Fermi momentum and $\xi_0=v_F/\Delta_0$ is the coherence length($\hbar=1$). In particular we find that the number of bound states decreases rapidly for decreasing $p_F\xi_0$. Also for $p_F\xi_0\sim 1$, the Kramer-Pesch effect stops around $T/T_c\simeq 0.3$.