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(a) Schematic diagram of quantum dot exciton states in the case of confining potential of low symmetry. , , and denote the crystal ground state and two linearly polarized exciton states, respectively. The fine-structure splitting of the linearly polarized eigenstates is denoted . denotes the exciton energy . (b) Schematic diagram of excitation by -polarized light of dot 1(2) charged with spin-up(down) electron. Dot 1(2) can absorb light only.
(a)–(c) Dependence of differential transmission on pump-probe delay for -polarized pump and -polarized probe [solid(open) symbols, respectively]. Black curves in (b) and (c) are fits using Eq. (1). (a) Calculations using Eq. (1). Solid symbols and the black curve show (see text) calculated for 80% and 0% of charged dots in the dot ensemble. (b) and (c) Measured pump-probe curves for samples of type [annealed for at , (b)] and [annealed for at , (c)]. (d) Dependences of the degree of circular polarization on the pump-probe delay measured for the sample of (c) at different spectral positions within the inhomogeneously broadened peak of the QD ground state (shown with circles on the corresponding PL spectrum in the inset).
(a) Dependences of the degree of circular polarization on the pump-probe delay measured for two samples of type annealed for 2.5 and (black and gray symbols, respectively). (b) and (c) Dependences of charging levels on the annealing time in samples of type (b) and (c). Dashed lines in (b) and (c) are guides for the eye.
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