Phys. Rev. X (in the press); preprint at

Sometimes, even physicists succumb to folklore. This typically arises when plausible, sometimes even rigorous arguments are widely understood to mean a particular phenomenon cannot arise under certain conditions. The 'impossibility' of isolating two-dimensional sheets of carbon is a prime example from the pre-graphene days.

A similar folk theorem seems to have taken hold in the study of the non-equilibrium quantum dynamics of many-body systems, the phenomenon known as many-body localization (MBL): based on perturbative arguments, it is generally thought that MBL is only possible in systems with short-range interactions.

Now, Rahul Nandkishore and Shivaji Sondhi have put forward a set of non-perturbative arguments to show that MBL can also arise with long-range interactions. The key idea is that they can drive the system into a non-trivial correlated phase, which is naturally described in terms of emergent degrees of freedom with only short-range interactions. The arguments are most rigorous in one dimension, but can be extended to two and three dimensions as well. MBL may therefore be more widespread than previously thought.