Regulation mechanism of broadband weakly epsilon‐negative response interpreted via Cu/CaCu ₃ Ti ₄ O ₁₂ metacomposites

Finely tuning spectral characteristics of the epsilon‐negative ( ε ′ < 0, EN) response is full of challenges when its regulatory mechanism in metacomposites is not yet clear. Herein, we have meticulously designed Cu/CaCu 3 Ti 4 O 12 (Cu/CCTO) percolative metacomposites, successfully achieved both epsilon‐negative and ε ′‐near‐zero (ENZ) responses in the radio‐frequency band. Before percolation, a large number of electric dipoles in the metacomposites achieved resonance characteristics near the ENZ point under the excitation of radio frequency electromagnetic fields, and as the Cu content increased, the ENZ frequency varied from 942, 858, 862 to 632 MHz. Further increasing the Cu content, accompanied by increasing intensity of the dielectric resonance, until concentration of electric dipoles reaches a critical value, the resonance disappears, and plasmonic oscillations appear. We obtained the broadband weakly EN response (| ε ′|< 100) at ~ 500 MHz–1 GHz region which was illustrated by Drude model. We further employed equivalent circuit and electromagnetic simulation to reveal the intrinsic inductance characteristics of EN response and demonstrated the existence of a sudden change in capacitance‐inductance at the ENZ, where energy fluctuations are accompanied by the transition of carriers from isolated dipole states to free plasmonic states. Our work provides a reference for revealing the broadband weak EN and ENZ response mechanisms, and will promote the application of metacomposites in electromagnetic shielding and novel sensors.