Multielectron Bubbles in Liquid Helium

Multielectron bubbles (MEBs) are cavities in liquid helium that contain electrons and possibly vapour. They provide a versatile platform for exploring properties of interacting electrons in two dimensions in a regime of densities that has not been previously available. Since the electrons are pushed against the deformable curved inner surface of the bubble, MEBs also provide an environment to study the roles of curvatures. In this review, we describe the current understanding of MEBs, with a focus on their stability issues, and highlight recent experimental studies of this interesting system.