By combining an atomistic pseudopotential method with the configuration interaction approach, we predict the pressure dependence of the binding energies of neutral and charged excitons: X 0 (neutral monoexciton), X − and X + (charged trions), and XX 0 (biexciton) in lens-shaped, selfassembled In0.6Ga0.4As/GaAs quantum dots. We predict that (i) with applied pressure the binding energy of X 0 and X + increases and that of X − decreases, whereas the binding energy of XX 0 is nearly pressure independent.(ii) Correlations have a small effect in the binding energy of X 0 , whereas they largely determine the binding energy of X − , X + and XX 0 . (iii) Correlations depend weakly on pressure; thus, the pressure dependence of the binding energies can be understood within the Hartree-Fock approximation and it is controlled by the pressure dependence of the direct Coulomb integrals J. Our results in (i) can thus be explained by noting that holes are more localized than electrons, so the Coulomb energies obeyThe energetics of excitons reflects a balance between single-particle energy levels E (e) and E (h) of electrons (e) and holes (h) in the system, and the many-particle carrier-carrier interactions, resulting from electron-hole Coulomb and exchange interactions.1,2,3 The variation of excitonic energies under pressure naturally reflects the corresponding variations in single-vs many-particle energies. Of particular interest are the pressure variations of excitons confined to nanosize dimensions such as in quantum dots. 4,5,6,7,8,9,10,11,12,13,14 Unlike the case of excitons in higher-dimensional systems, where binding and its pressure dependence reflects mostly manyparticle (correlation) effects, in zero-dimensional (0D) systems where the geometric dimensions are smaller than the excitonic radius, binding of neutral and charged excitons results from an interesting interplay between singleparticle and many-particle effects. Here, we use a realistic description of both single-particle and many-body effects in self-assembled In 0.6 Ga 0.4 As/GaAs quantum dots, showing how pressure affects the different components of exciton binding. We distinguish the neutral monoexciton X 0 (one e, one h), from the neutral biexciton XX 0(two e, two h), positive trion X + (one e, two h) and negative trion X − (two e, one h). While the effect of pressure on X 0 has been measured, 8,9,10,11,12,13 to the best of our knowledge, the optical spectroscopy of X − , X + and XX 0 under pressure has not yet been reported. For these reason, we provide definite predictions of the pressure effects. Each of the q-charged excitons has a spectrum of levels {ν}, of which the lowest is termed the "ground state of χ q " (χ = X, XX). This spectrum is usually expressed by expanding the many-body excitonic states |Ψ (ν) (χ q ) via a set of Slater determinants |Φ(χ q ) . The latter are constructed from single-particle electron and hole states and accommodate as many carriers as are present in χ q . The single-particle states are solutions to the effective Schrödinge...

Electron-hole exchange interactions split the exciton ground state into "dark" and "bright" states. The dynamics of those states depends on the internal relaxation time between bright and dark states (spin-flip time), and on the radiative recombination time of the bright states. On the other hand, the calculated values of these recombination times depend not only on the treatment of correlation effects, but also on the accuracy of the electron and hole wavefunctions. We calculate the radiative decay rates for monoexcitons and biexcitons in (In,As)Ga/GaAs self-assembled and colloidal CdSe quantum dots from atomistic correlated wave functions. We show how the radiative decay time τR(X 0 ) of the monoexciton depends on the spin-flip relaxation time between bright and dark states. In contrast, a biexciton has no bright-dark splitting, so the decay time of the biexciton τR(XX 0 ) is insensitive to this spin-flip time. This results in ratios τR(X 0 )/τR(XX 0 ) of 4 in the case of fast spin flip, and a ratio of 2 in the case of slow spin flip. For (In,Ga)As/GaAs, we compare our results with the model calculation of Wimmer et al. [M. Wimmer et al., Phys. Rev. B 73, 165305 (2006)]. When the same spin-flip rates are assumed, our predicted τR(X 0 )/τR(XX 0 ) agrees with that of Wimmer et al., suggesting that our treatment of correlations is adequate to predict the ratio of monoexciton and biexciton radiative lifetimes. Our results agree well with experiment on self-assembled quantum dots when assuming slow spin flip. Conversely, for colloidal dots the agreement with experiment is best for fast spin flip.PACS numbers: