Abstract
Biexcitons feature prominently in various scenarios for utilization of quantum dots (QDs) for enhancing the efficiencies of solar cells, and for the generation of entangled photon pairs in single QD sources. Two-dimensional double quantum coherence (2D-DQC) nonlinear optical spectra provide novel spectroscopic signatures of such states beyond global intensity and lifetime characteristics which are available by more conventional techniques. We report the simulation of a prototype 2D-DQC optical experiment of a self-assembled InAs/GaAs dot. The simulations consider the QD in different charged states and are based on a state-of-the-art atomistic many-body pseudopotential method for the calculation of the electronic structure and transition dipole matrix elements. Comparison of the spectra of negatively charged, neutral, and positively charged QD reveals optical signatures of their electronic excitations. This technique directly accesses the biexciton ($XX$) energies as well as the projections of their wave functions on the single-exciton manifold. These signals also provide a unique tool for probing the charged state of the QD and thus the occupation of the quantum state. Signatures of Pauli blockade of the creation of certain single and two excitons due to charges on the particles are observed. For all quantum states of the QD, the spectra reveal a strong multiconfiguration character of the biexciton wave functions. Peak intensities can be explained by interference of the contributing Liouville space pathways.
Published Version
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