Ultralow‐Frequency Epsilon‐Near‐Zero States in 3D‐Printed High‐Entropy Alloy Metacomposites for Ultra‐Thin Perfect RF Absorption
Peitao Xie, Haikun Wu, Zhenxiang Cheng, Mei Liu, Y. X. Liu, Y. X. Liu, Weikong Pang, Runhua Fan, Y. X. Liu, Y. X. Liu
Abstract
Epsilon-near-zero (ENZ) materials with radio-frequency perfect absorption are pivotal for next-generation electromagnetic stealth, 5G (fifth-generation mobile networks) signal integrity, and IoT (internet of things) security. Here, 3D-printed metacomposites achieving low-frequency ultra-thin ENZ absorption (>90%, 55-110 MHz, d/△λ<1/2455) are realized by confining high-entropy alloy (HEA) nanoparticles within hierarchically ordered porous carbon (HOPC). This hierarchical design leverages HEA's flattened band structures to maximize electron effective mass, while interfacial electron redistribution at HEA-carbon boundaries delocalizes charges and reduces carrier concentration. These dual effects synergistically suppress plasma frequency to 72.4 MHz, converting strong negative permittivity into near-zero states. A cocktail effect is discovered for reducing the plasma frequency with increasing the entropy. Concurrently, resonant enhancement from three complementary mechanisms-surface plasmons at HEA@graphitic core-shell interfaces, interfacial polarization in PU/HOPC heterojunctions, and hierarchical pore-cavity modes-boosts positive permittivity. Engineered cancellation of weakened negative permittivity and reinforced positive permittivity enables an ultra-broadband |ε'|<1 response spanning 55-110 MHz. The ENZ-mode perfect absorption of ultra-thin thickness, ultralow frequency, angle robustness, and broad band is achieved eventually. This work establishes a new paradigm for breaking the Rozanov limit via material-genesis ENZ engineering, bypassing artificial metamaterial arrays.