Sub-Doppler laser cooling of fermionic 40 K atoms in three-dimensional gray optical molasses

We demonstrate sub-Doppler cooling of 40 K on the D 1 atomic transition. Using a gray-molasses scheme, we efficiently cool a compressed cloud of 6.5 × 10 8 atoms from ∼4 mK to 20 μ K in 8 ms. After transfer to a quadrupole magnetic trap, we measure a phase space density of ∼10 −5 . This technique offers a promising route for fast evaporation of fermionic 40 K.