Magnetically tunable and enhanced spin Hall effect of reflected light in a multilayer structure containing anisotropic graphene

Abstract

In this paper, the magnetically tunable and enhanced photonic spin Hall effect (PSHE) of reflected light beam at terahertz frequencies is achieved by using a multilayer structure where anisotropic graphene is inserted. This enhanced PSHE phenomenon results from the excitation of surface plasmon polariton (SPP) at the interface between two dielectric materials. By considering the 4×4 transfer matrix method and the quantum response of graphene, the PSHE of the reflected light can be enhanced by harnessing the anisotropic conductivity of graphene. Besides, the PSHE can be tuned through the external magnetic field and structural parameters. This enhanced and tunable PSHE approach is promising for fabricating anisotropic graphene-based terahertz spin devices and other applications in nanophotonics.

Active manipulation of the plasmonic induced asymmetric photonic spin Hall effect

“…To investigate the APSHE induced and enhanced by the graphene SPP, a general model will be established to describe the APSHE of reflected beam in the graphene-based structure as shown in figure 1. This structure uses a multilayered coupling prism configuration which is similar to the [26,33,34]. Figure 1(a) is a schematic illustration of the wave reflection in a Cartesian coordinate frame.…”

“…It is well known that the graphene surface conductivity σ becomes a 2 × 2 tensor under a uniformly tunable magnetic B, which can be written as [26,33,34]…”

“…, where E f , k B and T are Fermi energy, Boltzmann's constant and temperature, correspondingly. The Fermi-Dirac distribution is sensitive to Fermi energy, which is important to note that the Fermi energy can be dynamically changed by adjusting the external electric field [34,44].…”

“…Compared to the SPP in metal materials, the graphene surface polaritons have great advantages in the enhancement and manipulation of the photonic SHE due to the tunability by gating or doping, wide operating bandwidth and low losses [28,33]. Yin et al theoretically achieved easier control of spin splitting shift by the excitation of the graphene SPP [34]. Due to the strong adsorption characteristic of graphene, several graphene-based plasmonic sensors with the tunable photonic SHE have been proposed [35,36].…”