Sounds and turbulence in a 2D Bose gas

I will discuss our recent experiments on driven box-trapped 2D Bose gases. We have observed first and second sound in this system, which is the first such observation in a Berezinskii-Kosterlitz-Thouless (BKT) superfluid. The measured speeds of the two sounds allow extraction of the superfluid density, which agrees with the expected universal jump at the critical point. I will also discuss our new results on strongly driven 2D gases in which a direct turbulent cascade emerges.