Stark-Wannier states and Bender-Wu singularities

Abstract
The authors present a numerical analysis of the Stark-Wannier states in finite Kronig-Penney crystals extended to the complex field plane. Exponential stability in the infinite crystal limit for any fixed complex field value f is verified. The energies En.j(f) of such states are all connected through sequences of couples of branch points of the Bender-Wu type approaching symmetrically the real axis. On the other hand, near f=0 in the complex directions they have a smooth behaviour and it is possible to compute the first terms of the asymptotic power series.

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