Complexes of Indirect Excitons in Layered Quasi-2D Heterostructures

We discuss trion and biexciton complexes formed by indirect excitons in layered quasi-2D semiconductors. Indirect excitons – long-lived neutral Coulomb-bound pairs of electrons and holes of different monolayers – were reported recently for bilayer graphene[1] and transition metal dichalcogenide systems[2]. We use the configuration space method[3] to derive the binding energies for the trion and biexciton complexes of indirect excitons as functions of the interlayer separation distance. The method captures essential kinematics of complex formation to reveal that, despite a rapid decrease with distance, the binding energies of both complexes can be significant – up to a few tens of meV – for (typical) interlayer distances ~3-5 Å, with the trion always having a greater binding energy than the biexciton. Trions and biexcitons formed by indirect excitons control the formation of more complex Wigner-like electron-hole crystal structures which are of great interest for spin-optronics applications[4,5]. -- [1]J.I.A.Li, et al., Nat. Phys.13,751(2017); [2]M.Baranowski, et al., NL17,6360(2017); [3]I.V.Bondarev, Mod. Phys. Lett.B30, 1630006(2016); [4]G.J.Schinner, et al., PRL110, 127403(2013); [5]J.S.Ross, et al., NL17,638(2017).