Anderson Janotti (University of Delaware)

November 8, 2019 @ 1:30 pm – 2:30 pm

Title: Emergent Phenomena at the Interface of Complex Oxides

Host: Cyrus Dreyer

Progress in epitaxial growth of complex oxides have led to heterostructures with exquisite physical phenomena, such as the formation of a high-density two-dimensional electron gas (2DEG) at the interface between two normally insulating materials—e.g. SrTiO3/LaAlO3. Superconductivity and magnetic ordering have been demonstrated in these systems, sparking the interest in novel device applications. The formation of a 2DEG at the interface between SrTiO3 and Mott insulators, such as GdTiO3, has also been demonstrated, with electron densities that are over an order of magnitude higher than those realized with conventional semiconductors. Charge transport in these systems exhibit intriguing behavior, varying drastically from metal to insulator depending on the thickness of the building-block layers. Intensive research efforts in the last decade have raised questions regarding the origin of the excess charge, the mechanisms that determine the density of the 2DEG, and fundamental properties of the 2DEG. In this presentation, we will discuss how computer simulations can provide insights into the origin and nature of the 2DEG. Based on results of first-principles calculations we will discuss electron correlation effects and how the electronic structure of these heterostructures can be drastically altered, turning from metallic into insulating, through charge localization in ultrathin layers. Finally, we will address the interplay between orbital, charge, and spin in the manipulation of the magnetic ordering observed in some of these heterostructures.

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