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.