Dali Sun

Strong coupling between two quantized excitations leads to a hybridized state that allows for exploring new phenomena and technologies. Phononic excitations, such as long-lived, high-overtone acoustic waves, can host many well-isolated modes at the same frequency. Meanwhile, magnetic excitations or magnons in magnetically-ordered materials show frequency tunability and can strongly couple with phonons. In this study, using the combination of analytical model, epitaxial growth, and spectroscopy characterization, we design a hybrid magnon-phonon cavity based on the La_0.7Sr_0.3MnO₃/SrTiO₃ (LSMO/STO) heterostructure with magnetoelastic coupling at the interface. Ferromagnetic resonance (FMR) measurements demonstrate strong coupling between the Kittel magnon of LSMO and the standing wave of transverse acoustic phonon of STO, as evidenced by their anticrossings in the FMR spectra. Remarkably, when the STO undergoes a cubic-to-tetragonal phase transition at T_S~105 K, the Kittel magnon of LSMO splits into three bands due to the anisotropic strains along the [100], [010], and [001] crystalline orientations, forming a network of hybrid magnon-phonon modes that are sensitive to strain engineering. Our work highlights high-quality magnetoelastic heterostructures as a suitable material platform to implement magnon-phonon hybrids, holding the promise of storing, encoding, and transducing coherent information between magnon and phonon modes.

Biography:

Dr. Sun’s research interests are in spintronics and optoelectronics of organic semiconductors, magnetic thin films, and organic-inorganic hybrid perovskites. It includes the studies of organic spin valves, organic light-emitting diodes, hybrid perovskite optoelectronic/spintronics devices, and their device physics. The Sun Research Group at NC State focuses on exploring novel routes for spin injection and detection, magnetic field effect, spin Hall effect and their applications in molecules, polymers and newly emerged materials.

Address:United States

Seonghwan Kim

Extensive engineering nanomaterials and their composites have been synthesized and introduced over the last two decades for various applications. Among them, metal-organic frameworks (MOFs), one-, two-, or three-dimensional crystalline structure materials consisting of metal cluster nodes and organic linkers, have attracted much attention due to their highly ordered nature, tunable pore volume, ultrahigh porosity, and the ability to tailor the frameworks’ chemical functionality by modifying the organic ligands. Over the last eight years, my research group has developed multiple MOFs and nanocomposite materials for physical and chemical sensing applications. Here, I will first introduce rapid and facile synthesis of MOFs and their composites on top of various sensing devices for gas/vapor sensing. In addition, chemical sensors based on colorimetric and fluorescent MOFs and other nanomaterials will be presented as cheap and rapid sensing platforms for the detection of trace amount of explosives, chemical warfare agents, and toxic ions in water. Lastly, MOF reinforced, high performance hydrogel or organohydrogel will be introduced and their applications as self-powered wearable strain/pressure sensors and triboelectric nanogenerators will be presented.

Biography:

Dr. Seonghwan (Sam) Kim is a full Professor and Tier 2 Canada Research Chair Laureate in the Department of Mechanical and Manufacturing Engineering at the Schulich School of Engineering, University of Calgary. He received his B.Sc. (1998) and M.Sc. (2000) degrees in Aerospace Engineering from Seoul National University, Seoul, South Korea, and his Ph.D. (2008) in Mechanical, Aerospace, and Biomedical Engineering from the University of Tennessee, Knoxville, USA. He was a Postdoctoral Research Associate at Oak Ridge National Laboratory, USA, and an Acting Research Associate at the University of Alberta prior to joining the University of Calgary in 2013.

Address:United States

Aron Cummings

In nano- and mesoscale systems, defects and disorder play a fundamental role in determining material properties and device performance. Such defects and disorder often present themselves on the atomic or sub-nanometer scale, while resulting transport length scales or device sizes can be orders of magnitude larger, on the micron scale. To accurately quantify and predict material properties or device performance in such situations, one often needs modeling and simulation tools that can bridge the size gap between atomic-scale defects and micron-scale systems. In this talk, I will present our group’s linear-scaling quantum transport tool, called LSQUANT. Based on the Kubo transport formalism, this tool combines accurate tight-binding models with an efficient expansion of quantum operators to allow the simulation of transport in systems containing many millions of atoms. This enables an atomic description of defects and disorder while still resolving transport properties on the experimental scale. After an introduction to the LSQUANT methodology, I will present a few examples of its application to transport in graphene, including spin and charge transport in disordered single-layer graphene and graphene nanoribbons, as well as approaches to optimize the performance of graphene photodetectors. Time permitting, I will also discuss recent efforts to update the LSQUANT methodology to study energy absorption and emission and the time-resolved dynamics of systems driven out of equilibrium, with an eye toward applications in photodetection, sensing, and optical communications.

Biography:

Dr. Aron W. Cummings is a Senior Researcher in the Theoretical and Computational Nanoscience group at the Catalan Institute of Nanoscience and Nanotechnology (ICN2) in Barcelona, Spain. He obtained a B.S. in Computer Engineering and a M.S. in Electrical Engineering at Washington State University, and a Ph.D. in Electrical Engineering at Arizona State University. He was a postdoc at Sandia National Laboratories in California, and at ICN2 before becoming a Senior Researcher in 2015. His research focuses on the numerical simulation of the transport of charge, spin, and heat in low-dimensional materials and devices.