Supersolids: what and where are they ?

TL;DR

This paper reviews the concept of supersolidity, focusing on solid helium-4, discussing theoretical frameworks, experimental evidence, and potential detection methods, including simulations and ultracold atom systems.

Contribution

It provides a comprehensive theoretical framework for supersolidity, reviews experimental findings in solid helium-4, and explores alternative detection approaches using ultracold atoms.

Findings

Extended defects like dislocations may underlie supersolidity.

First-principles simulations support theoretical models.

Ultracold atom assemblies offer alternative supersolid observation methods.

Abstract

The ongoing experimental and theoretical effort aimed at understanding non-classical rotational inertia in solid helium, has sparked renewed interest in the supersolid phase of matter, its microscopic origin and character, and its experimental detection. The purpose of this colloquium is a) to provide a general theoretical framework for the phenomenon of supersolidity and b) to review some of the experimental evidence for solid Helium-four, and discuss its possible interpretation in terms of physical effects underlain by extended defects (such as dislocations). We provide quantitative support to our theoretical scenarios by means of first principle numerical simulations. We also discuss alternate avenues for the observation of the supersolid phase, not involving helium but rather assemblies of ultracold atoms.