Hydrodynamic fluctuations melt crystals.

Consider an elastic lattice and drive it with a homogeneous fluid flow. At first sight this problem might sound trivial: isn’t the crystal merely advected by the flow? In this talk I will show that this seemingly simple question reveals a dramatic role of hydrodynamic interactions in confined liquids. Using microfluidic experiment, we demonstrate how hydrodynamic interactions causes the melting of elastic crystaline emulsions even at zero temperature. Unlike in equilibriium, we show that flow-induced melting of soft crystals does not obey the KTHNY scenario. Instead, melting is a one step process taking the form of a 1st order nonequilibrium transition where macroscopic crystals generically coexist with an isotropic liquids phase.