Event Details

Charge-ordered phases permeate the phase diagrams of strongly correlated systems such as layered transition-metal dichalcogenides, colossal magnetoresistive manganites and cuprate high-temperature superconductors. In such charge ordered states, modulations of the electron density break lattice translational symmetry and induce periodic lattice displacements via electron—lattice coupling. Bulk measurements have shown complex interactions between charge order and electronic phases, including direct competition with superconductivity or mediation of colossal magnetoresistance, however, the microscopic structure and origin of charge-ordered states remains actively debated.

In this talk, I will discuss room temperature and cryogenic scanning transmission electron microscopy techniques that have enabled direct mapping of the nature and evolution of charge order in manganites. We measure picometer-scale displacive modulations of the cations, distinct from existing manganite charge-order models, and reveal temperature-dependent phase inhomogeneities in the modulations, such as shear deformations and topological defects. At temperatures well below Tc phase coherence emerges. Our observations underscore the importance of lattice locking in manganites and provide a visualization of the real space structure of incommensurate order. More broadly, cryogenic STEM can now be used to investigate and quantify the role of the lattice in a variety of low temperature electronic phases.