Gold-coated graphene-embedded micron-sized polystyrene core–shell structures with an unconventional Hall anomaly and Berry curvature

Abstract

Unusual quantum phenomena in graphene are driven by non-zero Berry curvature and orbital magnetization. Herein, gold-coated monolayer graphene embedded in micron-sized polystyrene core–shell structures were successfully synthesized via a three-step method in order to break various symmetries for the first time. It is found that the Hall anomaly can be driven by a twist angle in the range of 0 < θ_c ≤ π/2. The plasmon resonance crossovers occur at the twist angle θ_c = π/4, for a ferromagnetic chiral edge with a Hall ratio of 3/4, correlated with the non-trivial edge with a Hall ratio of 1/3. The XRD test indicates that Au-intercalated graphene exhibits large Berry's twist angles of 38.2°, 44.4°, 64.6°, and 77.5°, together with indications of chiral edge states consistent with an icosahedral quasicrystal undergoing scale-dependent symmetry breaking in a ferromagnetic state. The distributed Bragg reflector (DBR) is primarily a result of bigraphene sheets, while the UV absorption plateau is shifted from 290 nm to 490 nm for the double plasmon resonances at transitions. Raman intensities reveal Hall ratios of 3/4, 5/2, 1/3, and 3/2, indicating the coexistence of ferromagnetism in bilayer graphene, and topological bands and correlated states in trilayer graphene. FTIR spectra display narrow valleys near 700 cm⁻¹, 1500 cm⁻¹, and 3000 cm⁻¹. This reveals the band-gap opening caused by chiral-symmetry breaking in low-energy excitations. Our findings present an opportunity to engineer graphene moiré physics.