Basic Science

Achievements in FeSe Superconductor

Science (332, 1410 (2011)) published on June 17th a new achievement in the research of iron-based superconductor Fese electron pairing symmetry co-made by a research team led by Ma Xucun from the Surface Physics Lab, Beijing National Laboratory (in the pipeline) of Condensed Matter Physics, Institute of Physics, CAS, in cooperation with the research team led by Xue Qikun from the Department of Physics, Tsinghua University. In order to deepen the research into a vital issue of Fese electron pairing symmetry, the research teams meticulously observed the STS (dI/dV, proportional to the state density of samples) of Fese film under extreme low-temperature. They discovered that dI/dV spectrum of Fese film has the characteristic of “V” pattern in 0.4k, directly proving that there exists energy gap zero-line in the Fese pairing function. More importantly, through collecting PSTM spectrum images under zero-bias, it can be observed directly in real space the quantized flux of Fese film, bound state of flux center and evolution law of bound state in space. The evolution of both single flux and bound state in space show double symmetry, which definitely confirms that the electron pairing function of FeSe has double symmetry. The further experimental results of space distribution of impurity state and impurity scattering also tested and verified the conclusion above. They have also theoretical cooperation with Prof. Wu Congjun of the University of California at San Diego to propose that the damage of FeSe electron paring quadruple symmetry may be related to the recombination of electronic structure on which the orbit depends.