Vortices as fractons

Abstract

Fracton phases of matter feature local excitations with restricted mobility. Despite the substantial theoretical progress they lack conclusive experimental evidence. We discuss a simple and experimentally available realization of fracton physics. We note that superfluid vortices form a Hamiltonian system that conserves total dipole moment and trace of the quadrupole moment of vorticity; thereby establishing a relation to a traceless scalar charge theory in two spatial dimensions. Next we consider the limit where the number of vortices is large and show that emergent vortex hydrodynamics also conserves these moments. Finally, we show that on curved surfaces, the motion of vortices and that of fractons agree; thereby opening a route to experimental study of the interplay between fracton physics and curved space. Our conclusions also apply to charged particles in a strong magnetic field. Fractons are phases of matter featuring particles with restricted mobility and represent a new paradigm of quantum condensed matter physics; but observing them experimentally is a challenge. Here, the authors demonstrate a simple platform for the realisation of fracton physics with vortices of a two-dimensional superfluid.