Sub-Doppler cooling in grey molasses - second life for laser cooling techniques

In the early days of laser cooling of atomic gases, unexpectedly low temperatures were discovered in different laboratories across the world. A new cooling mechanism, called Sisyphus cooling, proposed by J. Dalibard and C. Cohen-Tannoudji, explained these findings and led later to Nobel Prize in physics awarded to C. Cohen-Tannoudji in 1997. Unfortunately, this elegant mechanism doesn’t apply for all atomic species used in ultracold atoms experiments. However, last year a beautiful extension of Sisyphus cooling has been realized exactly for those unfortunate species for which the usual mechanism fails to work. In my talk I will describe the mechanism, called “grey molasses”, and show the experimental results.