General Physics Colloquium and Parratt Lecture, Dr. Jacob Ruff, CHESS, Cornell University

Refreshments from 3:30-3:50 pm

Title:  Uncovering Emergent Local Correlations in Materials with X-rays

Host:  Carl Franck

Abstract:  Crystal structure determination provides ground truth for materials physics. The process is relied upon so thoroughly that structures derived from diffraction measurements are commonly referred to as solutions, a term rarely used by experimentalists otherwise. However, many materials only approximate the perfect crystal ideal, and manifest emergent symmetries on local length scales that are not rigorously described by any of the 230 space groups. There are, in other words, many types of structures that we do not yet know how to solve. In this colloquium, I will outline the physical importance of local and incommensurate superstructures in materials. I will also survey new approaches that are being developed to measure, identify, and understand them using comprehensive x-ray studies at synchrotrons.