Abstract: The properties of quantum materials are determined by their structure across multiple length scales. Recently, spatial heterogeneities have been observed from a wide range of quantum materials, where nanoscale lattice deformations deviate from the ensemble average. Such heterogeneities sometimes organize in a hierarchical, almost self-similar manner, highlighting the necessity to incorporate both the real and reciprocal space in the description of lattice orders. Revealing and understanding how such hierarchical orders affect local and macroscopic material properties becomes an urgent request for developing new materials with improved properties.

In this talk, I will discuss our recent exploration of the spatial ordering heterogeneities using coherent nanodiffraction and X-ray photon correlation spectroscopy, with a focus on two materials with hierarchical orders of electric dipole polarizations, (1-x)PbMg_1/3Nb_2/3O₃-xPbTiO₃ and PbTiO₃-SrTiO₃ superlattice. Using coherent X-ray diffraction, we were able to visualize both static morphology and dynamic evolution of such hierarchical orders. I will also discuss new opportunities resonant soft X-ray scattering can bring for probing emerging magnetic and orbital orders. 

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.