Topological edge state coupled mode-induced tetra-band tunable spin-dependent perfect absorption

When discussing the spin-dependent optical perfect absorption (PA) phenomenon in a micro-nano structure, the designed structure should contain symmetry-breaking compositions that generally require an applied magnetic field. Fortunately, the multi-Weyl semimetal (mWSM) with natural time-reversal symmetry breaking property provides feasible schemes to investigate the spin-dependent PA without an external magnetic field. Recently, most existing schemes are primarily restricted to single- or dual-band spin-dependent PA in mWSM-based systems. Here, we present a heterostructure comprising five one-dimensional photonic crystals (PCs) and four identical mWSM layers to discuss the tetra-band spin-dependent PA. Results show that, due to the topological edge state-coupled mode and the nonzero off-diagonal term of mWSM, the PA of left-hand circularly polarized and right-hand circularly polarized light is attained at four distinct frequencies, respectively. More importantly, the tetra-band spin-dependent PA phenomenon can be regulated effectively via the tilt degree of Weyl cones, Fermi energy, topological charge, Weyl nodes separation, mWSM thickness, and the periods of the middle three PCs. This study provides an efficient scheme to achieve tetra-band adjustable spin-dependent PA without an external magnetic field, which may have potential applications in spin-dependent photonic devices.