Electric-field-controlled modulation of physical properties of materials via ionic evolution is a recent fascinating and fast developing research frontier, due to its novel phase modulation and potential applications in batteries, intelligent glass, fuel cells and etc. In a work published as cover article of Science Bulletin recently, researchers reported their efforts to implant protons into iron-based superconductors, using ionic liquids as the electrical medium.
They have succeeded in implanting protons into the 11 and the 122 structural compounds. Protonation induces bulk superconductivity with Tc at 20 K in undoped BaFe2As2, and two high-Tc phases with Tc at 42.5 K and 20 K in FeSe0.93S0.07, and enhances Tc from 4 K to 18 K in FeS. As a significant example, proton NMR measurements in FeS are enabled with evidences of unconventional superconductivity, overcoming the difficulty of lacking sensitive NMR isotopes. Therefore, protons serve a double role of dopant for carrier doping and a sensitive NMR isotope in bulk materials. This protonation methodology is easy to operate, could be immediately applicable to a wide range of materials for exploring insulating, metallic, or superconducting phases, and allows for rich bulk spectroscopic studies in the emergent phases.
See the article:
Yi Cui, Gehui Zhang, Haobo Li, Hai Lin, Xiyu Zhu, Hai-Hu Wen, Guoqing Wang, Jinzhao Sun, Mingwei Ma, Yuan Li, Dongliang Gong, Tao Xie, Yanhong Gu, Shiliang Li, Huiqian Luo, Pu Yu, Weiqiang Yu. Protonation induced high-Tc phases in iron-based superconductors evidenced by NMR and magnetization measurements. Science Bulletin, 2018, 63(1) 11-16, doi:10.1016/j.scib.2017.12.009
Hideo Hosono. Superconductivity induced by field-driven proton injection. Science Bulletin, 2018, 63(1) 5-6, doi: 10.1016/j.scib.2018.01.009