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Manipulating electronic structure and transport in correlated oxide heterostructures

In complex transition metal oxides, strong correlations between electrons lead to entangled ground states with many fascinating emergent phenomena, including magnetism and high-­‐ temperature superconductivity. Moreover, the interplay between structural, charge, spin, and orbital degrees of freedom in these systems opens up the possibility of inducing and influencing exotic phase behavior using state-­‐of-­‐the-­‐art atomic layering techniques. In this talk, I describe the engineering of electronic structure and transport properties of complex oxides through atomically-­‐precise control of dimensionality and interfacial structure using molecular beam epitaxy. Specifically, I focus on two studies related to the rare-­‐earth nickelates, an archetypal correlated system. The first investigation concerns the thickness-­‐induced metal-­‐insulator transition in LaNiO3, in which we use synchrotron-­‐based x-­‐ray diffraction and  magnetotransport to reveal the structural origin of the crossover and demonstrate the realization of two-­‐dimensional conduction in LaNiO3 by surface engineering. The second   project focuses on our ability to manipulate the orbital configuration in rare-­‐earth nickelates. A combination of first-­‐principles theory and synchrotron-­‐based x-­‐ray techniques illustrates that unique three-­‐component heterostructuring can be used to effectively change the nickelate orbital structure to emulate that of the high-­‐temperature superconducting cuprates, and, in   fact, can tune the orbital configuration between the bulk structures. Both approaches are based on simple physical mechanisms and represent routes to explore and enhance a wide variety of orbitally-­‐dependent phenomena in correlated oxides including metal-­‐insulator transitions, spin switching and superconductivity.

Ankit Disa is a PhD candidate in Applied Physics in the group of Prof. Charles Ahn at Yale University. He received his B.S. in Applied and Engineering Physics from Cornell University in 2010.