  Optical trapping and ions combine unique advantages of independently striving
fields of research. Light fields can form versatile potential landscapes, such
as optical lattices, for neutral and charged atoms, avoiding detrimental
implications of established radiofrequency (rf) traps while mediating
interaction via long range Coulomb forces, controlling and detecting motional
and electronic states on the quantum level. Here we show optical trapping of
$^{138}$Ba$^{+}$ ions in the absence of rf fields in a far-detuned dipole trap,
suppressing photon scattering by three and the related recoil heating by four
orders of magnitude. To enhance the prospects for optical as well as hybrid
traps, we demonstrate a novel method for stray electric field compensation to a
level below 9 mV/m. Our results will be relevant, for example, for ion-atom
ensembles, to enable four to five orders of magnitude lower common
temperatures, accessing the regime of ultracold interaction and chemistry,
where quantum effects are predicted to dominate.
