报 告 人：陈晓嘉 研究员
Xiao-Jia Chen was awarded his Ph. D from Zhejiang University in 1997. He has both theoretical and experimental expertise in the study of superconductivity, magnetism, and hydrogen-bearing materials at high pressures. He is a staff scientist of Center for High-Pressure Science and Technology Advanced Research (HPStar) of China and a director of Center for Energy Matter at Extreme Environments of The Chinese Academy of Sciences. He also holds a joint scientist position of HPStar and U.S. Carnegie Institution of Washington’s Geophysical Laboratory. He has been serving as a leader of superconductivity program of U.S. Department of Energy’s Energy Frontier Research in Extreme Environments Center (EFree) since 2009, where his research led to the discovery of the enhanced superconductivity at higher pressure in cuprates, the re-emergence of superconductivity at higher pressure with much higher Tc than the ambient value in iron-based superconductors, and the enhanced magnetoelectric coupling in multiferroric materials. His current research at HPStar focuses on the discovery of new superconductors in light element bearing systems and the improvement of the performance of known superconductors by understanding the fundamental physics of superconductivity. He has published over 80 papers in popular scientific journals including Nature and its research journals and Physical Review Letters.
Abstract: One of the most remarkable phenomena in condensed matter science is the sudden, total disappearance of electrical resistance of many metals, alloys, and compounds as the temperature is lowered through a material-specific critical temperature. Currently, iron-based superconductors are classified as the second family exhibiting high-temperature superconductivity after copper oxides. Pressure plays an essential role in inducing or tuning superconductivity as well as shedding insight on the mechanism of superconductivity. Choosing three typical iron-based series Ba1-yKyFe2-xAxAs2 (A=Ni, Co), Fe1+ySe1-xTex, and AxFe2-ySe2 (A=K, Rb, Tl), we investigate pressure effects on the physical properties of these superconductors with the emphasis of physics after superconductivity is completely destroyed. Based on the multiple technique measurements, we establish extended pressure - temperature phase diagrams for these compounds. Contrary to the general belief of the existence of Fermi liquid after the disappearance of superconductivity upon compression, we find an unexpected insulating state in some heavily compressed compounds. Reentrance of superconductivity is also discovered and the new superconducting phase has been identified. These results indicate that rich physics is still hidden in iron-based superconductors.