Applied Physics and Materials Science Special Seminar

Abstract:

Quantum-mechanical effects and strong electron-electron interactions give rise to solids with superb electronic properties and a vast potential for future technologies. In many of these strongly interacting materials, electrons self-organize into new spatial patterns that break the symmetry of the underlying crystal. A grand challenge in the field is to understand the nature of these symmetry-breaking states and to overcome their tendency to form inhomogeneous textures at the nanoscale. Towards that goal, atomic-resolution transmission electron microscopy techniques hold immense promise for advancing quantum materials research; however, progress has been hindered by the lack of low-temperature capabilities that are necessary to study quantum systems.

Here I will show vivid atomic-scale visualizations of electronic order in strongly correlated oxides unleashed by the development of cryogenic scanning transmission electron microscopy (cryo-STEM). This novel technique enables direct visualizations of (i) the picoscale atomic displacements governing electronic transitions in quantum materials, (ii) the nature and symmetry of charge/orbital order, and (iii) a complex nanoscale landscape involving topological defects, phase competition, and inhomogeneity. Finally, I will describe our recent and unique approach that has enabled cryogenic electron microscopy with liquid helium cooling and atomic resolution. These capabilities pave the way for novel explorations of ultra-low temperature quantum phenomena in the electron microscope.

More about the Speaker:

Ismail El Baggari is a Principal Investigator and Fellow at the Rowland Institute at Harvard. He obtained his Ph.D. and M.S. in Physics from Cornell University working with the late Prof. Lena Kourkoutis and a Bachelor of Science in Applied Physics from Yale University. His research focuses on the development of in situ cryogenic electron microscopy for understanding quantum materials and devices.