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X-WR-CALDESC:Events for UNAM Nanoteknoloji Araştırma Merkezi
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DTSTART:20220101T000000
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BEGIN:VEVENT
DTSTART;TZID=Europe/Moscow:20220615T123000
DTEND;TZID=Europe/Moscow:20220615T133000
DTSTAMP:20260907T164410
CREATED:20220614T062227Z
LAST-MODIFIED:20220614T062629Z
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SUMMARY:Probing leaky and guided exciton-polaritons in resonant planar structures
DESCRIPTION:Anton Samusev\nITMO University \n\nPlanar periodic structures such as metasurfaces and photonic crystal slabs strongly coupled to an exciton resonance attract particular attention since they provide vast opportunities for on-demand engineering of the dispersion of guided and leaky polariton resonances. In this regard\, experimental characterization and control of the over modes’ dispersion is of great importance. In this talk\, I will show both what new physical phenomena appear in such systems and how these effects can be directly observed in the experiment. \nIn the first part of the talk\, I will show an experimental approach allowing to retrieve the real [1\, 2] or even full complex [3] dispersion of both leaky and evanescent waves in arbitrary planar structures. The method is based on back focal plane microspectroscopy combined with a solid immersion lens (SIL) separated from the sample by a precisely controlled nanoscale air gap (Otto geometry). Varying the gap allows for extracting both real and imaginary parts of the wavenumber of surface waves propagating in an arbitrary in-plane direction. \nIn the second part of the talk\, I will switch gears to another implication of dispersion engineering in planar structures – the possibility of realization of strong light-matter coupling regime with excitons in transition metal dichalcogenides [4\, 5] and perovskites [6]. I will highlight the nonlinear [4\, 6] and topological [5] properties of exciton polaritons in such systems enabled by finely tuned custom designs of the photonic band structure. \nFinally\, we will discuss how to directly observe and analyze guided exciton-polaritons in planar waveguides either made of a perovskite or based on high-index dielectric slab integrated with transition metal dichalcogenide monolayer. I will show how direct variation of radiative losses via changing the SIL-sample distance in such systems allows for the control of Rabi splitting\, and extraction of exciton-photon coupling strength along with the intrinsic properties of excitons in the sample under study. \nReferences\n1. Pidgayko\, D.\, Sinev\, I.\, Permyakov\, D.\, Sychev\, S.\, Heyroth\, F.\, Rutckaia\, V.\, Schilling J.\, Lavrinenko A.\, Bogdanov A. and Samusev\, A.\, “Direct imaging of isofrequency contours of guided modes in extremely anisotropic all-dielectric metasurface”\, ACS Photonics\, Vol. 6\, No 2\, 510-515\, 2018.\n2. Permyakov\, D. V.\, Sinev\, I. S.\, Sychev\, S. K.\, Gudovskikh\, A. S.\, Bogdanov\, A. A.\, Lavrinenko\, A. V. and Samusev\, A. K.\, “Visualization of isofrequency contours of strongly localized waveguide modes in planar dielectric structures”\, JETP Letters\, vol. 107\, No 1\, 10-14\, 2018.\n3. Permyakov\, D. V.\, Kondratiev\, V. I.\, Pidgayko\, D. A.\, Sinev\, I. S. and Samusev\, A. K.\, “Probing Optical Losses and Dispersion of Fully Guided Waves through Critical Evanescent Coupling”\, JETP Letters\, vol. 113\, No 12\, 780-786\, 2021.\n4. Kravtsov\, V.\, Khestanova\, E.\, Benimetskiy\, F. A.\, Ivanova\, T.\, Samusev\, A. K.\, Sinev\, I. S.\, Pidgayko\, D. A\, Mozharov\, A. M.\, Mukhin\, I. S.\, Lozhkin\, M. S.\, Kapitonov\, Yu. V.\, Brichkin\, A. S.\, Kulakovskii\, V. D.\, Shelykh\, I. A.\, Tartakovskii\, A.I.\, Walker\, P. M.\, Skolnick\, M. S.\, Krizhanovskii \, D. N. and Iorsh\, I. V.\, “Nonlinear polaritons in a monolayer semiconductor coupled to optical bound states in the continuum”\, Light: Science & Applications\, Vol. 9\, No. 1\, 1-8\, 2020.\n5. Li\, M.\, Sinev\, I.\, Benimetskiy\, F.\, Ivanova\, T.\, Khestanova\, E.\, Kiriushechkina\, S.\, Vakulenko\, A.\, Guddala\, S.\, Skolnick\, M.\, Menon\, V. M.\, Krizhanovskii\, D.\, Alù\, A.\, Samusev\, A. and Khanikaev\, A. B.\, “Experimental observation of topological Z2 exciton-polaritons in transition metal dichalcogenide monolayers”\, Nature communications\, Vol. 12\, No 1\, 1-10.\n6. Masharin\, M. A.\, Shahnazaryan\, V. A.\, Benimetsky\, F. A.\, Krizhanovskii\, D. N.\, Shelykh\, I. A.\, Iorsh\, I. V.\, Makarov S.V. and Samusev\, A. K.\, “Polaron-enhanced polariton nonlinearity in lead halide perovskites”\, arXiv preprint arXiv:2201.10265\, 2022 \n  \n  \nAbout The Speaker\nAnton Samusev holds the position of Assistant Professor at School of Physics and Engineering\, ITMO University\, St. Petersburg\, Russia. Since the PhD defense in 2011 at Ioffe Institute\, St. Petersburg\, Russia\, he is leading a scientific group currently comprising 3 Assistant Professors\, 4 Postdocs\, PhD\, MS and BS students. The scientific interests of the group lie at the confluence of the fields of nanooptics\, solid state and laser physics. The research topics include experimental studies of the near- and far-field properties of optically resonant nanoantennas and metasurfaces weakly or strongly coupled to 2D and 3D materials with pronounced excitonic response (transition metal dichalcogenides\, perovskites)\, dispersion engineering of optical surface waves in structured media\, phase change materials\, topological photonics\, photon emission from tunnel junctions\, single-photon emitters and others. Since 2017 Anton lectures the course “Introduction to Experimental Nanophotonics” within the “Nanophotonics and metamaterials” MS program at ITMO University. \nJoin Zoom Meeting\nhttps://zoom.us/j/5876884794?pwd=OUNFRTZKZDNRMm5MWjJjSlhnMXFNUT09https://zoom.us/j/95581724217 \n\n \n 
URL:https://unam.bilkent.edu.tr/en/event/6648/
CATEGORIES:UNAM Seminars
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DTSTART;TZID=Europe/Moscow:20220623T153000
DTEND;TZID=Europe/Moscow:20220623T170000
DTSTAMP:20260907T164410
CREATED:20220614T110849Z
LAST-MODIFIED:20220614T111212Z
UID:6659-1655998200-1656003600@unam.bilkent.edu.tr
SUMMARY:Connecting Atomic-scale Impurities to Larger Morphologies
DESCRIPTION:Nadire Nayir\nKaramanoglu Mehmetbey University/The Pennsylvania State University \n\n(Half) van der Waals epitaxy of single-crystal two-dimensional (2D) materials (e.g.\, TMD\, h-BN\, graphene\, group III materials) on substrates are quite challenging and time and source expensive. Therefore\, theoretically characterization of materials is essential to deepen our understanding of the physical and chemical properties of materials\, thus\, ensuring the highest quality in the design and manufacturing processes of materials.\nThis talk will first focus on our multiscale modeling efforts for the synthesis and characterization of 2D materials. I will show some of our own results which have been dedicated to addressing the major challenges encountered in experiments such as (i) unidirectional alignment of 2D domains on a substrate\, (ii) impact of the surface chemistry and crystallographic structure of a substrate on the van der Waals epitaxy\, (iii) unraveling gas-phase chemistry in chemical vapor deposition environment\, (iv) impact of growth conditions on the crystal structure of 2D materials. Additionally\, since technology is developing faster than ever before\, and increasingly depends on constantly advancing basic research and expanding scientific knowledge\, an effective-force field development for multicomponent systems has become crucial to accelerate the knowledge transfer to industry. In the second part\, this talk will also provide an overview of the ReaxFF force fields and multiscale model framework that we developed for 2D materials [4-6]. These potentials offer a computationally cost-effective and versatile research tool for the materials science community to study large-scale simulations of synthesis and defect-\, phase-\, strain-\, and edge engineering of a material of interest\, paving the way for increased application of atomic-level modeling of 2D materials. In turn\, new computational materials and new knowledge will benefit the society by advancing new technologies in energy conversion\, storage\, and other important areas. \n  \n1. N. Nayir\, M. Y. Sengul\, A. L. Costine\, P. Reinke\, S. Rajabpour\, A. Bansal\, A. Kozhakhmetov\, J. Robinson\, J. M. Redwing\, A. van Duin\, “Atomic-scale probing of defect-assisted Ga intercalation through graphene using ReaxFF Molecular Dynamics Simulations”\, Carbon\, 190\, 276–290 (2022)\n2. DR Hickey\, N Nayir\, M Chubarov\, TH Choudhury\, S Bachu\, L Miao\, Y. Wang\, C. Qian\, V. H. Crespi\, J. M. Redwing\, A. C. T. van Duin\, N. Alem “Illuminating Invisible Grain Boundaries in Coalesced Single-Orientation WS2 Monolayer Films”\, Nano Letters 21 (15)\, 6487-6495 (2021)\n3. N. Briggs\, B. Bersch\, Y. Wang\, J. Jiang\, R. J. Koch\, N. Nayir\, K. Wang\, M. Kolmer\, W. Ko\, A. D. L. F. Duran\, S. Subramanian\, C. Dong\, J. Shallenberger\, M. Fu\, Q. Zou\, Y. Chuang\, Z. Gai\, A. Li\, A. Bostwick\, C. Jozwiak\, C. Chang\, E. Rotenberg\, J. Zhu\, A. C. T. van Duin\, V. Crespi\, J. A. Robinson\, “Atomically thin half-van der Waals metals enabled by confinement heteroepitaxy”\, Nature Materials 19 (6)\, 637-643 (2020) 4. N. Nayir\, Y. K. Shin\, Y. Wang\, M. Y. Sengul\, D. Reifsnyder Hickey\, M. Chubarov\, T. H Choudhury\, N. Alem\, J. Redwing\, V. H Crespi\, A. CT van Duin\, “A ReaxFF Force Field for 2D-WS2 and Its Interaction with Sapphire”\, The Journal of Physical Chemistry C 125 (32)\, 17950-17961 (2021) 5. N. Nayir\, Y. Wang\, Y. Ji\, T. Choudhury\, J. M. Redwing\, L.-Q. Chen\, V. H. Crespi\, A. C. T. van Duin\, “Theoretical Modeling of Edge-controlled Growth Kinetics and Structural Engineering of 2D-MoSe2”\, Materials Science and Engineering: B 271\, 115263 (2021)\n6. Y. Xuan\, A. Jain\, S. Zafar\, R. Lotfi\, N. Nayir\, Y. Wang\, T. H. Choudhury\, S. Wright\, J. Feraca\, L. Rosenbaum\, J. M. Redwing\, V. Crespi\, A. C. T. van Duin\, “Multi-scale modeling of gas-phase reactions in metal-organic chemical vapor deposition growth of WSe2”\, Journal of Crystal Growth 527\, 125247 (2019) \n \nAbout The Speaker\nNadire Nayir is currently a postdoctoral research associate of Physics at Karamanoglu Mehmetbey University and a research affiliate of the 2-dimensional Crystal Consortium (2DCC) at The Pennsylvania State University. She received her BS in physics education from Selcuk University in 2009\, and Ph.D. in computational physics from Middle East Technical University in 2018. She worked as a postdoctoral associate of Mechanical Engineering at The Pennsylvania State University for 3 years. \nJoin Zoom Meeting\nhttps://zoom.us/j/5876884794?pwd=OUNFRTZKZDNRMm5MWjJjSlhnMXFNUT09https://zoom.us/j/95581724217 \n\n  \n 
URL:https://unam.bilkent.edu.tr/en/event/connecting-atomic-scale-impurities-to-larger-morphologies/
CATEGORIES:UNAM Thursday Seminars
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