Physics Colloquium


Speaker(s): Divine Kumah, North Carolina State University

The ability to control and probe orbital, electronic, and spin degrees of freedom in two-dimensional transition-metal oxides has led to the discovery and understanding of a wide range of condensed matter phenomena including high-temperature superconductivity, Mott metal-insulator transitions, emergent magnetism, strongly correlated behavior, and quantum critical phenomena. Progress in the field has been driven by advances in the atomic-scale synthesis of crystalline two-dimensional multilayered systems, where strain and interfacial interactions can be systematically tuned to realize novel electronic and magnetic ground states. Additionally, the development of high-resolution synchrotron X-ray diffraction and spectroscopy techniques allows for non-destructive and in-operando probes of materials to elucidate structural and electronic changes at interfaces between dissimilar oxide films.
> To illustrate the intimate link between interface-driven atomic-scale distortions and the physical properties of low-dimensional systems, this talk will focus on understanding the role interfacial and surface reconstructions play in driving experimentally observed thickness-dependent metal-insulator and magnetic transitions in the 3d and 4d transition metal oxide systems.[1,2,3] Guided by first-principles theory, the talk will highlight how atomic-scale materials growth techniques and state-of-the-art methods to characterize their physical properties at the picometer-scale, provide a powerful approach for discovering novel quantum materials.
> Bio: Divine Kumah is an Associate Professor in the department of Physics at North Carolina State University. He received his Ph.D in Applied Physics from the University of Michigan in 2009 and did postdoctoral research at the Center for Research in Interface and Surface Phenomena at Yale University. His research interests are in experimental condensed matter physics and are aimed at understanding the novel properties which emerge at the interfaces between crystalline materials.
> The Kumah Research Group at NC State uses state of the art atomic layer-by-layer deposition techniques including molecular beam epitaxy to fabricate thin crystalline oxide films. The group is focused on understanding how atomic-scale structural distortions at interfaces can be manipulated to induce novel electronic and magnetic phenomena and the development of pathways for harnessing these unique functionalities for electronic and energy applications. Tools used by the group include atomic force microscopy, electron diffraction and synchrotron-based x-ray spectroscopy and diffraction.



Darlene McCain