Neutron Scattering Study of Low Energy Spin Excitations in the FeTe/Se Superconductors

Zhijun Xu (University of California, Berkeley)

Spin fluctuations are believed to play an essential role in the phase diagrams and transitions in both the recently discovered Fe-based superconductors and the high-Tc cuprates. Inelastic neutron scattering is a powerful tool for studying magnetism in superconductors; it can provide important information on the momentum and energy dependence of the magnetic excitations in these materials. Similar to the case of the high-Tc cuprates, a spin-resonance and spin-gap can be present in Fe-based superconductors when the system enters the superconducting phase. Here I will present results suggesting that in addition to these common signatures, a dramatic change in the low energy spin excitation spectrum is observed in the Fe(Te/Se) superconductor ("11" compounds). The low energy spin excitations from the superconducting and non-superconducting phases in this system are distinctively different over the entire Brillouin zone; this is related to a change of the spin correlations in the material driven by temperature and/or doping. Implications of these results and possible future work will be discussed.

A short bio:
Zhijun Xu was born in Shanghai, China in 1981. He obtained his B.Sc. (2004) from Fudan University in China, and Ph.D. (2011) from the graduate school and university center of CUNY (City University of New York) in the U.S. He was a research associate (2011-2013) at Brookhaven national laboratory and a postdoctoral scholar at UC Berkeley since 2013. He has worked on growth of large high-quality single crystal and studying materials properties using neutron scattering. Understanding the magnetic and lattice structures and dynamics in complex materials systems such as high-Tc superconductors, multiferroics, and ferroelectrics are current main areas of his research.

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