Observation of a giant Goos-H\"anchen shift for matter waves

TL;DR

This paper reports the observation of a giant Goos-H"anchen shift for matter waves, specifically neutrons, using a neutron spin-echo technique and magnetic multilayer mirrors, revealing a resonant enhancement linked to waveguiding effects.

Contribution

The study demonstrates the first measurement of a giant GH shift for matter waves, utilizing a novel experimental setup with magnetic multilayers and neutron spin-echo techniques.

Findings

Resonant enhancement of GH shift at specific neutron wavevector

Propagation distance of 0.65 mm along the waveguide layer

Confirmation of GH shift through neutron absorption in the waveguide layer

Abstract

The Goos-H\"anchen (GH) shift describes a phenomenon in which a specularly-reflected beam is laterally translated along the reflecting surface such that the incident and reflected rays no longer intersect at the surface. Using a neutron spin-echo technique and a specially-designed magnetic multilayer mirror, we have measured the relative phase between the reflected up and down neutron spin states in total reflection. The relative GH shift calculated from this phase shows a strong resonant enhancement at a particular incident neutron wavevector, which is due to a waveguiding effect in one of the magnetic layers. Calculations based on the observed phase difference between the neutron states indicate a propagation distance along the waveguide layer of 0.65 mm for the spin-down state, which we identify with the magnitude of the giant GH shift. The existence of a physical GH shift is confirmed by the observation of neutron absorption in the waveguide layer. We propose ways in which our experimental method may be exploited for neutron quantum-enhanced sensing of thin magnetic layers.