Ultracold atoms in optical lattices have become a key tool for the testing of fundamental concepts of condensed matter physics, allowing in particular to simulate the behaviour of electrons in solid crystals. A quantum-gas microscope with single-atom and single-lattice-site resolution furthermore allows for the measurement of the properties of equilibrium many-body quantum states and out-of-equilibrium dynamics with direct probing of e.g. the local entropy distribution or spin-spin correlation functions.
In our experiment, we realise the fluorescence imaging of fermionic potassium-40 atoms with a quantum-gas microscope. Efficient cooling of 40K is required to reach the strongly-correlated regime and to perform the imaging of atoms in the lattice. This has led us to the development of a grey molasses cooling technique on the D2 line of potassium [1] and the use of electromagnetically-induced-transparency (EIT) cooling for the fluorescence imaging [2].
I will present both cooling techniques, and the single atom images we obtained, as well as the latest developments in the experiment towards the strongly-correlated regime of fermions on a lattice.
[1] J. Phys. B, 50, 095002 (2017)
[2] Nature Physics 11, 738–742 (2015)