EAGER: Tuning Orbital Order in Nickelate Superlattices with Atomic Layer-by-Layer Growth using Laser Molecular Beam Epitaxy (MBE)

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NON-TECHNICAL DESCRIPTION: The mechanism that leads to the high temperature superconductivity in a family of layered copper oxides has been an active area of research since its discovery in 1986. Recently, it has been predicted theoretically that the electronic structure in the high temperature superconducting cuprates can be realized in lanthanum nickelate when it is sandwiched between insulating oxide such as lanthanum aluminate in the so-called superlattices. Both the lanthanum nickelate and lanthanum aluminate layers need to be very thin, just two atomic layers. Proving or disproving this prediction can not only help understand the mechanism of high temperature superconductivity, but potentially lead to discovery of new high temperature superconductors in cuprates, nickelates, and other material systems. The goal of this project is to fabricate the nickelate superlattices by atomic layer-by-layer growth using laser molecular beam epitaxy and measure their electronic structure properties and superconductivity to test the theoretical prediction. Success of the project can significantly advance the knowledge in the areas of strongly correlated transition metal oxides, materials by design, and nanoscale engineering of oxide heterostructures. The project supports a female graduate student for her Ph.D. degree, thus directly broadens the participation of underrepresented groups. TECHNICAL DETAILS: This EAGER grant focuses on tuning orbital order in nickelate superlattices by atomic layer-by-layer growth using laser molecular beam epitaxy. Recently, it has been predicted theoretically that using reduced dimensionality and epitaxial strain the electronic structure in the high-Tc superconducting cuprates can be realized in lanthanum nickelate by sandwiching it between insulating oxide such as lanthanum aluminate in superlattices where each period contains one unit cell of each materials. Doping could then induce superconductivity. No experimental proof has been reported despite numerous efforts and the validity of the theoretical prediction has been questioned. This project uses a new film deposition technique, laser molecular beam epitaxy from separate oxide targets, to achieve the atomic layer-by-layer growth of the nickelate superlattices. This approach is more appropriate than the growth techniques that have been attempted in tuning the orbital order and inducing superconductivity in the nickelate superlattices. The success of the project can significantly advance the knowledge in the areas of strongly correlated transition metal oxides, materials design, and nanoscale engineering of oxide heterostructures. The project provides multidisciplinary training for a female graduate student, directly broadening the participation of an underrepresented group.