Magneto-optical measurements of semiconducting nanocrystals doped with rare-earth ions

The magneto-optical properties of semiconducting nanocrystals doped with transition metals, exhibiting strong spd spin-exchange effects, have been thoroughly studied; using rare earth elements as dopants offers a pathway to understanding spin-exchange interactions with electrons in f orbitals, instead. To study this interaction, there must be strong overlap between carrier and 4f dopant wavefunctions, while this is not possible in 2D or bulk semiconductors, it is ideal in 0D nanocrystals. This study uses Tb-doped CdSe nanocrystals which are characterized using three primary techniques to extract information about the spf interaction: magneto-photoluminescence, magnetic circular dichroism and time-resolved differential transmission. MCD measurements, a direct measure of the Zeeman splitting of excitonic states, exhibit a sign-flip, indicating the presence of a spf interaction. Magneto-PL measurements support this evidence through complementary data by instead studying the degree of circular polarization of the emitted light. Finally, time-resolved differential transmission measurements show a difference in carrier lifetimes between doped and undoped nanocrystals, further supporting the presence of spin-exchange interaction.