Bound States and Band Structure - a Unified Treatment through the   Quantum Hamilton - Jacobi Approach
  We analyze the Scarf potential, which exhibits both discrete energy bound states and energy bands, through the quantum Hamilton-Jacobi approach. The singularity structure and the boundary conditions in the above approach, naturally isolate the bound and periodic states, once the problem is mapped to the zero energy sector of another quasi-exactly solvable quantum problem. The energy eigenvalues are obtained without having to solve for the corresponding eigenfunctions explicitly. We also demonstrate how to find the eigenfunctions through this method. 
S. Sree Ranjani, A. K. Kapoor and P. K. Panigrahi