Calculation of Wannier-Bloch and Wannier-Stark states

The paper discusses the metastable states of a quantum particle in a periodic potential under a constant force (the model of a crystal electron in a homogeneous electric field), which are known as the Wannier-Stark ladder of resonances. An efficient procedure to find the positions and widths of resonances is suggested and illustrated by numerical calculations for a cosine potential, which are in excellent agreement with complex scaling resonance energies