Cooling of Atoms Using an Asymmetric One-Way Barrier

We show how to construct asymmetric optical barriers for atoms. These barriers can be used to compress phase space of a sample by creating a confined region in space where atoms can accumulate with heating at the single photon recoil level. We describe how the wall can be created with a simple two-level model and then show how it can be applied to more realistic multi-level atoms. The phase space compression is illustrated in two regimes: (i) when the wall is placed in the middle of a box potential and atoms are collected in the smaller region; (ii) when it is moved in the concave potential with a finite velocity. In both cases we derive analytical expression for compression and compare them with numerical simulations of collisonless gas.