Abstract The Goos–Hänchen (GH) effect, a longitudinal shift of a wave beam at total internal reflection, is well known in optics and has been repeatedly observed for light, micro-, and ultrasonic waves. We consider the GH effect for a massive particle reflected from a material boundary. A close relation is shown to exist between the longitudinal shift and the time delay of reflection. In the case of a neutron reflected from a planar resonant system, a giant longitudinal shift of either positive or negative sign can occur, corresponding to a large reflection group delay time. This time can also be negative, which does not contradict the causality principle. Prospects of the experimental observation of the GH effect and group delay time for neutron reflection are reviewed.
The Goos-Hanchen effect, a longitudinal shift of a wave beam at total inner reflection, is a well-known optical phenomenon. It was discovered in 1947 and have been observed many times at reflection of micro- and ultrasonic waves since then. Here we present an elementary theory of the GH. effect to describe reflection of a massive particle and demonstrate how the shift is related to delay time at reflection. It is shown that giant positive or negative longitudinal shifts of the neutron beam may occur at neutron reflection from some specially manufactured planar system. The possibility of delay time measurement at neutron reflection and direct experimental observation of the GH shift are also discussed.
We study the influence of an external magnetic field on the Goos-Hänchen (GH) shift and the group delay time (GDT) in monolayer WSe
2 in the presence of a magnetic barrier. The transport properties of Dirac-like carriers are obtained by solving the effective low-energy Hamiltonian and evaluating the corresponding transmission amplitudes. The GH shift and the GDT are subsequently extracted from the phase of the transmission coefficient. We systematically analyze their dependence on the magnetic field strength, incident energy, angle of incidence, and barrier width, with particular emphasis on the spin and valley degrees of freedom associated with the
K and
K′ valleys. Our results show that the magnetic barrier strongly modulates both the GH shift and the GDT, leading to oscillatory behavior and pronounced spin-valley-dependent transport characteristics. Remarkably, the magnetic field enables selective control of the lateral shift and traversal time of carriers for each spin and valley channel, allowing for tunable spatial and temporal separation of electronic wave packets. This provides a mechanism for manipulating fermionic trajectories after transmission through the barrier in a highly controllable manner. Such tunability opens promising avenues for designing nanoscale devices based on spin and valley filtering, as well as for potential applications in information storage and processing within spintronic and valleytronic platforms.