Sub-Doppler laser cooling of fermionic ${}^{40}\mathrm{K}$ atoms

We report laser cooling of fermionic ${}^{40}\mathrm{K}$ atoms, with temperatures down to $(15\mathrm{}\pm 5)\hspace{0.5em}\mu \mathrm{K},$ for an enriched sample trapped in a magneto-optical trap and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of 2 of the lowest realizable rms velocity $\left(\sim {3.5v}_{\mathrm{rec}}\right)$ in three-dimensional optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of ${}^{40}\mathrm{K}$ atoms.