Displacement operator for quantum systems with position-dependent mass
  A translation operator is introduced to describe the quantum dynamics of a position-dependent mass particle in a null or constant potential. From this operator, we obtain a generalized form of the momentum operator as well as a unique commutation relation for $\hat x$ and $\hat p_\gamma$. Such a formalism naturally leads to a Schr\"odinger-like equation that is reminiscent of wave equations typically used to model electrons with position-dependent (effective) masses propagating through abrupt interfaces in semiconductor heterostructures. The distinctive features of our approach is demonstrated through analytical solutions calculated for particles under null and constant potentials like infinite wells in one and two dimensions and potential barriers. 
R. N. Costa Filho, M. P. Almeida, G. A. Farias, and J. S. Andrade Jr
quant-ph cond-mat.other