  Carrier-dopant exchange interactions in Mn-doped PbS colloidal quantum dots
were studied by circularly polarized magneto-photoluminescence. Mn
substitutional doping leads to paramagnetic behavior down to 5 K. While undoped
quantum dots show negative circular polarization, Mn doping changes its sign to
positive. A circular polarization value of 40% was achieved at T=7 K and B=7
tesla. The results are interpreted in terms of Zeeman splitting of the band
edge states in the presence of carrier-dopant exchange interactions that are
qualitatively different from the s,p-d exchange interactions in II-VI systems.
