A new effective mass Hamiltonian and associated Lame equation: bound   states
  A new quantum model with rational functions for the potential and effective mass is proposed in a stretchable region outside which both are constant. Starting from a generalized effective mass kinetic energy operator the matching and boundary conditions for the envelope wave functions are derived. It is shown that in a mapping to an auxiliary constant-mass Schrodinger picture one obtains one-period ``associated Lame'' well bounded by two delta-wells or delta-barriers depending on the values of one ordering parameter. The results for bound states of this new solvable model are provided for a wide variation of the parameters. 
A. Ganguly, M.V. Ioffe and L.M. Nieto