In quantum materials strong interactions between the electrons and the atomic lattice can give rise to novel electronic states with properties not achievable in conventional materials. These states often compete with other correlated states of spin, charge and the atomic lattice. One example is charge ordering, in which electrons as well as the atomic lattice form periodic patterns that not only lift the symmetries of the crystal but also underlie exotic electronic phenomena such as superconductivity, metal-insulator transitions and colossal magnetoresistance. Understanding the microscopic nature of electron-lattice interactions at the relevant length scales at which quantum phenomena arise, and the role of disorder requires advanced spatially resolved probes.
In this talk, I will discuss our advances in scanning transmission electron microscopy (STEM) to probe emergent order in quantum materials at the atomic scale. First, I will discuss our results on a class of superconducting materials, the recently reported infinite-layer nickelates, with particular focus on the microscopic structure, strain and the role of defects in these thin film superconductors. Going beyond room temperature STEM, cryogenic sample cooling promises direct access to low temperature phases and quantum phase transitions. These new capabilities have paved a path to visualize subtle lattice and electronic orders in emergent low temperature phases as I will show in the second part of the talk. Focus will be on the lattice behavior of charge-ordered manganites, where direct imaging can discriminate between multiple structure models, and mapping over larger length scales shows phase coexistence and nanoscale inhomogenities.
Speaker: Lena Kourkoutis, Cornell University
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