Postgraduate research opportunities Laser cooling & Bose-Einstein condensation

Bose-Einstein condensates made by laser cooling and evaporative cooling of atoms are the coldest known substance and are beginning to find a wide range of applications from understanding fluids to precision measurements. Most Bose-Einstein condensate to date are based ‘one-electron atoms’, i.e. the atomic structure is determined by a single electron outside a charged core. This generally leads to an atomic structure ideal for laser cooling but without any particularly narrow spectral lines that would be ideal for precision measurement or optical clocks. On the other hand, the two-electron atoms (such a calcium) offer narrow lines associated with transitions, where an electron spin flips, and are still relatively easy to laser cool.

The narrow transition in atomic calcium is key in this project. It will enable us to laser cool the atoms all the way to Bose-Einstein condensation – something that has not been possible to do with other atoms. An essential part of this is to trap the atoms in the strong light field of a CO2 laser in order to prevent them from falling under gravity while they are slowly cooled on the narrow line.

The direct laser cooling to condensation is radically different from the traditional approach, which relies on atomic collisions. It will therefore provide new insight into the formation of condensates. The CO2 laser offers a wide choice of geometry for the condensate. We can generate condensates in 1, 2 and 3 dimensional lattices and study the interaction of many independently created condensates when they are allowed to ‘see’ each other due to quantum mechanical tunnelling through the separating barriers.