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.
We theoretically discuss the input–output characteristics of the cascaded magnon-photon system by focusing on the slow light effect caused by positive group delay. When two identical magnon-photon systems are cascaded, compared with the single cavity system, the bandwidth of the whole system is wider, but the group delay is smaller. The change of the group delay is different from that of the general linear system. Moreover, by changing the cavity length of the two microwave cavities, the system is slightly mismatched and the group delay could obviously increase. The slow light effect could be controlled by relative cavity length. The slow light effect of the mismatched double cavity system is more sensitive to external magnetic field than that of the single cavity system. The results provide a way to manipulate the transmission rate in optical information networks and a new view about the interconnection of microwave cavities.
The ability to slow down light at the single-photon level has applications in quantum information processing and other quantum technologies. We demonstrate two methods, both using just a single artificial atom, enabling dynamic control over microwave light velocities in waveguide quantum electrodynamics (QED). Our methods are based on two distinct mechanisms harnessing the balance between radiative decay and nonradiative decoherence rates of a superconducting artificial atom in front of a mirror. In the first method, we tune the radiative decay of the atom using interference effects due to the mirror; in the second method, we pump the atom to effectively control its nonradiative decoherence. When the half of the radiative decay rate exceeds the nonradiative decoherence rate, we observe positive group delay; conversely, dominance of the nonradiative decoherence results in negative group delay. Our results advance signal-processing capabilities in waveguide QED.