Local Structure Study of Fe-based Superconductors and Others by Using Neutron Scattering

by Prof. Keeseong Park (DGIST)

Wednesday Apr 10, 2013, 5:00 PM → 6:00 PM Asia/Seoul

120호 (제1과학관)

The pair density function method would be reviewed by using neutron scattering data of a topological insulator Bi2(Se/Te)3 from HIPD at Lujan neutron scattering center in Los Alamos. Various interesting local structure phenomena were found in the system including a local strain on a Se/Te layer, stacking fault of layers, and atomic site preference. Most of them are difficult to be observed from conventional Rietveld method. Local structure was carefully studied for Fe-based superconductors to find structural hints to reveal superconductivity. In Ba(FeCo)2As2, local disorder was found at the Co-overdoped region where the superconductivity disappears. A model based on a breathing mode was proposed to explain the disorder. In Fe(SeTe), local lattice dynamics was investigated related with superconductivity. The nearest Fe-Te/Se bonds may diminish around 25 meV. The nearest Fe-Fe pairs may split in the Se-rich superconducting compound but not in the Te-rich non-superconducting compound. Specially, the Fe-Fe pairs split at lower energy when the temperature decreases below the superconducting temperature.