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Speaker:  Yue Cao, Materials Science Division, Argonne National Laboratory 

Abstract:  

Our understanding of crystalline quantum materials relies critically on the notion of order parameters, which describe the correlation between electrons either in the real or reciprocal space, but usually not at the same time. Recently, spatial ordering inhomogeneities have been discovered across a wide range of quantum materials, highlighting the necessity to incorporate both the real and reciprocal space in the description of electronic and lattice orders. Revealing and understanding the heterogeneity is indispensable for connecting the atomic structure and macroscopic materials properties.

In 1939, William Bragg proposed an X-ray microscope that from today’s perspective can be used to probe the spatial hierarchies and heterogeneities of order parameters. Different realizations of his microscopes have become feasible recently owing to the enhanced photon coherence at X-ray facilities. In this talk, I will discuss our recent exploration of the spatial ordering heterogeneities using coherent nanodiffraction and X-ray photon correlation spectroscopy. This talk will be focused on two materials canonical in their respective class – charge and magnetically ordered perovskite La_1/3Sr_2/3FeO₃ and relaxor ferroelectric PbMg_1/3Nb_2/3O₃. We will show how nano- and mesoscale inhomogeneities shed insight into the structure-property relationship.

The work at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division, under Contract No. DE-AC02-06CH11357.

Host:  Jak Chakhalian