Physics Colloquium: Yohannes Abate, "Probing interactions at the nanoscale"
The Susan Dasher and Charles Dasher MD Professor of Physics
Department of Physics and Astronomy
University of Georgia. Athens, GA
Interactions at the nanometer length scale in hard and soft condensed matter give rise to intriguing phases in correlated electron materials, lead to the design of exotic metamaterials, and offer enormous opportunities for the development of novel optoelectronic devices. In this talk, I will give examples of high-resolution probing of nanoscale physical phenomena and interactions in quantum materials specifically correlated oxides and van der Waals (vdW) crystals. Correlated oxides provide exciting opportunities to reconfigure polaritonic devices at the nanoscale, due to their highly tunable local optical and electronic properties [1,4-6]. I will introduce a hybrid polaritonic-oxide heterostructure platform consisting of vdW crystals, such as hexagonal boron nitride or alpha-phase molybdenum trioxide, transferred on nanoscale oxygen vacancy patterns on the surface of correlated perovskite oxide SmNiO3 (SNO). Hydrogenation and temperature modulation allow spatially localized conductivity modulation of SNO nanoscale patterns, enabling robust real-time modulation and nanoscale reconfiguration of hyperbolic polaritons. We have developed a simulational methodology to calculate the nanoscale modulation of the dielectric response of SNO with respect to differing levels of hydrogenation and oxygen vacancy formation using a combination of Langevin dynamics and Metropolis Monte Carlo methods. Interaction of vdW crystals with oxygen and water in ambient environment leads to enhanced chemical reactivity of their extraordinarily high surface areas. Using a combination of hyperspectral tip-enhanced photoluminescence, Raman, and near-field nanoscopy I will present recent imaging and spectroscopy results that reveal exotic interface effects and oxidized species during photodegradation of 2D in-plane MoS2–WS2 heterostructures with nanoscale alloyed interfaces and thin flakes of allotropes of phosphorus (black and violet phosphorus)[2.3]. The 2D alloy interface coupled with intrinsic strain causes spatial inhomogeneity of the oxidation and emission of the various excitonic species, providing localized potential wells at corner interfaces for various charge carriers and enabling localized emission with enhanced stability.
1. N. A. Aghamiri, G. Hu, A. Fali, Z. Zhang, J. Li, S. Balendhran, S. Walia, S. Sriram, J. Edgar, S. Ramanathan, A. Alu, and Y. Abate, “Reconfigurable Hyperbolic Polaritonics with Correlated Oxide
Metasurfaces” Nature Comm. (Under Review), DOI:10.21203/rs.3.rs-947391/v1
2. A. Fali, M. Snure, and Y. Abate, “Violet phosphorus surface chemical degradation in comparison to black phosphorus” Appl. Phys. Lett. (Editor’s Pick), 118, 163105 (2021) DOI: 10.1063/5.0045090
3. A. Fali, T. Zhang, J. Terry, E. Kahn, K. Fujisawa, S. Koirala, Y. Ghafouri, W. Song, L. Yang, M. Terrones, Y. Abate, Y. Abate, “Photo-degradation Protection in 2D In-Plane Heterostructures Revealed by
Hyperspectral Nanoimaging: the Role of Nano-Interface 2D Alloys” ACS Nano 2021, 15, 2, 2447–2457 https://doi.org/10.1021/acsnano.0c06148
4. M. Kotiuga, Z. Zhang, J. Li, F. Rodolakis, H. Zhou, R. Sutarto, F. He, Q. Wang, Y. Sun, Y. Wang, N. A Aghamiri, S. B. Hancock, L. P. Rokhinson, D. P. Landau, Y. Abate, J. W. Freeland, R. Comin, S.
Ramanathan, and K. M. Rabe, “Carrier Localization in Perovskite Nickelates From Oxygen Vacancies” PNAS 201910490 (2019). https://www.pnas.org/content/116/44/21992
5. A. Fali, S. T. White, T. G. Folland, M. He, N. A. Aghamiri, S. Liu, J. H. Edgar, J. D. Caldwell ,R. F. Haglund, Y. Abate” Refractive Index-Based Control of Hyperbolic Phonon-Polariton Propagation” Nano
Letters 2019 19 (11), 7725-7734 DOI: 10.1021/acs.nanolett.9b02651
6. T. G. Folland, A. F., S. T. White, J. R. Matson, S. Liu, N. A. Aghamiri, J. H. Edgar, R. F. Haglund Jr., Y. Abate, J. D. Caldwell, Reconfigurable infrared hyperbolic metasurfaces using phase change materials.
Nature Communications 2018, 9. DOI: https://doi.org/10.1038/s41467-018-06858-y
Yohannes Abate is the Susan Dasher and Charles Dasher MD Professor of Physics at the University of Georgia. Abate’s condensed matter physics research interests include fundamental nanoscale physical phenomena and interactions in nano- and quantum- materials. His group implements various terahertz, infrared, and optical spectroscopy and imaging techniques with diffraction unlimited spatial resolution. His awards include NSF Career Award (2016), Scialog Collaborative Innovative Award, Research Corporation for Science Advancement (2015), Most Valuable Professor, California State University, Long Beach (2014), Luis Alvarez Award for Best Experimental Research (American Physical Society CA Section) (2008) and The 2000 International Publication Award (University of the Philippines, Diliman) (2000).
Professor Abate joined the University of Georgia (UGA) as an associate professor of physics in August 2017. He received his PhD in Physics at the University of Iowa in 2006. From 2006-2009 he was a postdoctoral research fellow at the University of California, Berkeley and Lawrence Berkeley National Laboratory. Before joining UGA faculty, he was a member of the faculty (2014-2017) at Georgia State University and (2009-2014) California State University.