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Condensed Matter Seminar feat. Igor Bondarev: "Strongly correlated collective excitations in planar transdimensional nanostructures"
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Thursday, December 17, 2020 - 11:30am to 12:30pm
Igor Bondarev (North Carolina Central University)
I will briefly review the latest experiments and then enlarge on our theoretical efforts to unravel the properties of hybrid quasi-2D semiconductor and metallic nanostructures, efforts that have uncovered their intriguing optical attributes. For instance, we show that charged and neutral exciton complexes in highly excited van der Waals bound transition metal dichalcogenide (TMD) heterostructures can have substantial binding energies, and can be controlled externally to form strongly-correlated long-range collective states. Exciton complexes in TMD systems are of interest for nonlinear optics and spinoptronics, and offer a new unconventional high-T superconductivity mechanism based on a charged Bose-Einstein condensate of quaternions. We also develop a theory of exciton intermixing and polarization dynamics for quasi-2D crystalline semiconductors of organic molecules. The nonlinear polarization response function we derive exhibits the dynamical reorientation of molecular exciton polarization, pointing out the charge separation direction in organic molecular chains. Finally, we study the confinement related effects in the optical response of isotropic and anisotropic finite-thickness plasmonic films in the transdimensional regime between 3D and 2D. We show the plasma frequency acquires spatial dispersion typical of 2D materials and gradually shifts to the red with the thickness reduction. This explains the experiments done on aligned carbon nanotube films and on TiN films.