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Physics Seminar: Exciton complexes in quasi-2D crystals in the configuration space approach
Prof. Igor V. Bondarev
North Carolina Central University
Durham, NC, USA
I will present a universal method for binding energy evaluation of the lowest energy neutral and charged exciton complexes (biexciton, trion) in spatially confined semiconductor nanostructures . The method, originally pioneered by Landau, Gor’kov, Pitaevski, Holstein, and Herring in their studies of molecular binding and magnetism, was first utilized for quasi-1D nanostructures to evaluate biexciton and trion binding energies in small-diameter carbon nanotubes . I will show that the method can also be used for the electron-hole complexes of indirect excitons in quasi-2D semiconductor systems such as coupled quantum wells and bilayer van der Waals bound transition metal dichalcogenide heterostructures. The method works in the effective configuration space of two relative electron-hole motion coordinates in two non-interacting spatially confined excitons. Biexciton and trion bound states form due to the under barrier tunneling of the electron-hole system between the equivalent configurations in the configuration space. Tunneling rate controls the binding strength and can be turned into the binding energy by means of an appropriate variational procedure. Exciton complexes in coupled quantum wells and bilayer van der Waals bound transition metal dichalcogenide heterostructures are of great interest for nonlinear optics and spin-optronics applications [3-5].
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 M.M.Fogler, L.V.Butov, and K.S.Novoselov, Nature Commun. 5, 4555 (2014).
 J.S.Ross, P.Rivera, J.Schaibley, et al., Nano Lett. 17, 638 (2017).