Quantum Goos-Hänchen switch in graphene junctions

Goos-Hanchen (GH) shift, an interference phenomenon describing the lateral shift of the reflected beam along the interface during total internal reflection, has attracted great interests in the field of quantum transport in two-dimensional materials. In particular, the GH effect generates a novel pseudospin-dependent scattering effect in graphene, which in turn results in an 8e2/h conductance step in the bipolar junctions. Here, we reveal that a barrier region with effective barrier strength chi can greatly enrich the GH effect in graphene junctions. In contrast to the conventional case where the negative shift is allowed only in the p-n junction, the thin barrier enables both negative and positive spatial shifts in pIn and nIn junctions, where I represents the barrier region. More interestingly, the lowest channel degeneracy can be efficiently varied by tuning chi in both the symmetric pInIp and the asymmetric pnIp junctions, leading to a highly controllable switch that switches the conductance between 8e2/h and 4e2/h . These results advance the knowledge of GH effects in electronic materials and suggest experimental avenues for its observation and manipulation.