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Abstract:
We consider the scattering of particles (kinetic energy epsilon) by an obstacle which tunnels coherently between two positions ( tunnel splitting Delta), for arbitrary values of epsilon/Delta and scattering strength U. The obstacle mimics two classical scatterers at fixed positions when epsilon less than or similar to Delta. Interference disappears when epsilon >> Delta, but can be recovered if the elastic-scattering channel is detected only. At intermediate values of there is a systematic interplay of the coherent tunnel motion and the ballistic particle motion. We show that the transmission probability can remain finite even in the limit U --> infinity because the particle can evade the obstacle systematically. We discuss the realization of a quantum obstacle in mesoscopic systems.
