  Radiofrequency traps are used to confine charged particles but are only
stable for a narrow range of charge-to-mass ratios. Here, we confine two
particles -- a nanoparticle and an atomic ion -- in the same radiofrequency
trap although their charge-to-mass ratios differ by six orders of magnitude.
The confinement is enabled by a dual-frequency voltage applied to the trap
electrodes. We introduce a robust loading procedure under ultra-high vacuum and
characterize the stability of both particles. It is observed that slow-field
micromotion, an effect specific to the dual-field setting, plays a crucial role
for ion localization and will be important to account for when engineering
controlled interactions between the particles.
