Biexciton Binding of Dirac fermions Confined in Colloidal Graphene Quantum Dots.

Sun, Cheng; Figge, Florian; Ozfidan, Isil; Korkusinski, Marek; Yan, Xin; Li, Liang-shi; Hawrylak, Pawel; McGuire, John A · Nano Lett · 2015

basic_science · Level V

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Abstract

We present transient absorption measurements and microscopic theory of biexciton binding in triangular colloidal graphene quantum dots consisting of 168 sp(2)-hybridized C atoms. We observe optical transitions from the lowest orbitally dark singlet exciton states to states below the energy of an unbound dark+bright singlet-exciton pair. Through microscopic calculations of the low-energy exciton and biexciton states via tight-binding, Hartree-Fock, and configuration interaction methods, the spectra reveal a biexciton consisting primarily of a dark-bright singlet-pair bound by ∼0.14 eV.

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