Tunable asymmetric spin splitting by black phosphorus sandwiched epsilon-near-zero-metamaterial in the terahertz region.

In-plane photonic spin splitting effect is investigated in tunneling terahertz waves through an epsilon-near-zero metamaterial sandwiched between monolayer black phosphorus (BP). The strong in-plane anisotropy of BP layers will induce in-plane asymmetric spin splitting. The asymmetric spin splitting can be flexibly tuned by the angles between the incident plane and the armchair crystalline directions of the top and bottom BP layers, i.e., ϕ1 and ϕ2. Based on this, an angle-resolved barcode-encryption scheme is discussed. For the special case of ϕ1 = ϕ2 = 0 or 90°, the transmitted beam undergoes Goos-Hänchen shift, which varies with the carrier density of BP. We believe these findings can facilitate the development of novel optoelectronic devices in the Terahertz region.