Materials Science & Technology Division
Oak Ridge National Laboratory
Exploring structural and electronic instabilities in high-Tc superconductors by high resolution scanning transmission microscopy and spectroscopy
Location: EB1 Room 1011
Friday, December 5th 2014 - 11:00 am
Many complex materials behaviors result from structural or chemical inhomogeneities with characteristic lengths that are too small to be resolved by diffraction techniques or other bulk-sensitive measurements. Aberration-corrected scanning transmission electron microscopy (STEM) yields real-space images of atoms or ion-columns in a solid, using an electron probe smaller than the average atom size and without the requirement that the structure be periodic. When coupled with electron energy-loss spectroscopy (EELS), STEM provides not only atomic structure but also electronic structure information atomic-column by atomic-column, allowing us to resolve nanometer-size inhomogeneities and probe the physics of interfaces, without incurring in misinterpretations due to averaging.
In this talk I will discuss the role of structural and chemical inhomogeneities in iron-based superconductors of the 122-arsenide and selenide family, and the phenomenon of high-Tc interfacial superconductivity arising at the interface between SrTiO3 and the insulating infinite layer compound CaCuO2.
I will also discuss the validity of a method for comparing local magnetic moments using the Fe-L2,3 EELS edge that can be adopted for many Fe- and transition-metal-compounds, and in principle used to map the local magnetic moment with sub-nanometer spatial resolution.