Issue 2, 2015 - China has developed hydrothermal iron-based superconducting materials

Recently, the National Institute of Nanotechnology and Engineering reported that China has made a major breakthrough in the field of nanotechnology, and the research group of Professor Chen Xianhui of the University of Science and Technology of China has successfully developed a new type of nanomaterial - iron-based superconducting material using hydrothermal method, and its superconducting transition temperature is as high as 40K or more, breaking through the limit temperature
of McMillan.
This is the first time that China has discovered a new type of FeSe high-temperature superconducting material by hydrothermal method, which is expected to end the long-term
dependence of superconducting materials on imports from the United States and Japan.

The research group of Professor Chen Xianhui of the University of Science and Technology of China successfully discovered a new FeSe superconducting material OHFeSe
with a superconducting transition temperature of more than 40K for the first time by using the hydrothermal reaction method.
The material is made of FeSe layer and OH layer alternately stacked in the c direction, and the FeSe layer and OH layer are connected
by extremely weak hydrogen bonds.
They also collaborated with several research groups including Dr.
Qingzhen Huang of the Neutron Research Center of the National Institute of Standards and Technology to accurately determine the crystal structure
of the new material by combining X-ray diffraction, neutron scattering and nuclear magnetic resonance.

It is understood that the researchers also found that the severely distorted FeSe4 tetrahedron in this structure is conducive to superconductivity, which is completely different
from the perfect FeAs4 tetrahedron in FeAs-like superconductors that favors superconductivity.
Specific heat, susceptibility and NMR data indicate that the new superconducting material has an antiferromagnetic sequence at a low temperature of 8.
5K and coexists
with superconductivity.
At the same time, the advantages of high superconducting transition temperature and air stability of the new superconductor set the direction for further experimental research, and also provided an ideal material system
for exploring the internal mechanism of iron-based high-temperature superconductivity.
(Section)