Observation of the Goos-Hänchen Shift with Neutrons

Abstract

The Goos-H\"anchen effect is a spatial shift along an interface resulting from an interference effect that occurs for total internal reflection. This phenomenon was suggested by Sir Isaac Newton, but it was not until 1947 that the effect was experimentally observed by Goos and H\"anchen. We provide the first direct, absolute, experimental determination of the Goos-H\"anchen shift for a particle experiencing a potential well as required by quantum mechanics: namely, wave-particle duality. Here, the particle is a spin-polarized neutron reflecting from a film of magnetized material. We detect the effect through a subtle change in polarization of the neutron. Here, we demonstrate, through experiment and theory, that neutrons do exhibit the Goos-H\"anchen effect and postulate that the associated time shift should also be observable.