In Situ Investigations of Functionality at Interfaces: Correlated Ions, Topological Insulators, and Ferroics

10:00 AM - 11:00 AM
Nouamane Laanait, Argonne National Laboratory, Argonne
Materials Science & Technology Division
Building 4100, Room J-302

Email: Gyula Eres

Modern investigations of interfacial phenomena occur at the intersection of condensed matter physics, materials science, and chemistry. An understanding of such rich and complex behavior necessitates fundamentally novel analytical approaches and experimental probes, examples of which are introduced in this talk. Interfacial systems offer exciting opportunities to address longstanding scientific questions in a controlled setting. This is illustrated by our work that demonstrates the presence of a strongly correlated layer of ions at electrified liquid/liquid electrolyte interfaces. A novel hybrid classical density functional theory is introduced to describe the microscopic and macroscopic responses of the system to the electric field, providing excellent agreement with thermodynamic measurements and scattering experiments. Immense progress has been achieved in the synthesis of interfacial systems using epitaxial thin films. Yet, the presence of mesoscale structure in these systems is prevalent, resulting from the penetration of interface coupling into the bulk materials. Using a newly developed X-ray diffraction microscope with large depth penetration, we show that by probing the local structure of a Bi2Se3 thin film and the buried interface with the 6H-SiC (0001) substrate, the growth modes can be investigated. We briefly discuss the role of this mesoscale structure, in the form of growth spirals, in modulating the electronic properties of the metallic surface states hosted by the topological insulator Bi2Se3. I will also present recent progress in imaging the local evolution of the structural phases in complex oxide thin films that display ferroic (PbTiO3) and multiferroic (BiFeO3) order parameters, as a function of external thermodynamic potentials. The responses exhibited by these systems showcase future opportunities in real-time investigations of materials in complex environments.


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