Jordan Hachtel1,Eric Hoglund1,Harrison Walker2,De Liang Bao2,Geemin Kim3,Mahmut Sami Kavrik4,Matt Law3,Sokrates Pantelides2
Oak Ridge National Laboratory1,Vanderbilt University2,University of California, Irvine3,Lawrence Berkeley National Laboratory4
Jordan Hachtel1,Eric Hoglund1,Harrison Walker2,De Liang Bao2,Geemin Kim3,Mahmut Sami Kavrik4,Matt Law3,Sokrates Pantelides2
Oak Ridge National Laboratory1,Vanderbilt University2,University of California, Irvine3,Lawrence Berkeley National Laboratory4
Over the last 5-10 years, the scanning transmission electron microscope (STEM) has been turned to quantum materials more and more due to the ability to correlate the subtle structural signatures of quantum phase transitions with atomistic imaging and compositional analysis. Over this same time period, monochromation for electron energy-loss spectroscopy (EELS) in the STEM has also seen a resurgence. With typical energy resolutions improving by two orders of magnitude to enable a whole host of new experiments at the high spatial resolution of the STEM. The combination of the two is truly a new opportunity for quantum materials, as it allows the ability to probe the novel quasiparticles and shallow electronic structure that mediate emergent phenomena directly at the length scales over which they occur.<br/><br/>In this talk, I will discuss the application of monochromated STEM-EELS to quantum nanostructured superlattices. In SrTiO<sub>3</sub>-CaTiO<sub>3</sub> (STO-CTO) superlattices, where the superlattice is in the growth direction with alternating layers of STO and CTO at different unit-cell thicknesses. In this system, the period of the superlattice dominates the macroscopic properties of the material through changing the number of interfaces between the STO and CTO. However, in short period superlattices, an emergent phonon response causes the interface-density-dependency to reverse and as the material takes a new property based off of the interface octahedral tilts. I will also discuss PbSe quantum dot superlattices, where the superlattice concerns lateral, self-assembled, epitaxially-connected quantum dots that form a network analog to a cubic crystal structure. Here the electronic states delocalize across the epitaxially connected QDs to create emergent electronic structure not present in the individual quantum dots. In both cases the combination of spatial and spectral information reveal emergent spectroscopic repsonses in the nanostructured superlattice.