We have synthesized two Nb@C composites with an order of magnitude difference in the density of single-atom niobium substituted into graphitic layers. The concentration and sites of single-atom Nb are identified using aberration-corrected scanning transmission electron microscopy and density functional theory. Comparing the complex permittivity spectra show that the representative dielectric resonance at ~16 GHz originates from the intrinsic polarization of single-atom Nb sites, confirmed by theoretical simulations. The single-atom dielectric resonance represents the physical limit of the electromagnetic response of condensed matter, and thus might open up a new avenue for designing electromagnetic wave absorption materials. Single-atom resonance also has important implications in understanding the correlation between the macroscopic dielectric behaviors and the atomic-scale structural origin.
@article{arxiv.1507.01557,
title = {Gigahertz Dielectric Polarization of Single-atom Niobium Substituted in Graphitic layers},
author = {Xuefeng Zhang and Junjie Guo and Pengfei Guan and Gaowu Qin and Stephen J. Pennycook},
journal= {arXiv preprint arXiv:1507.01557},
year = {2015}
}