A Perspective on Collective Properties of Atoms on 2D Materials

TL;DR

This paper explores the potential for atoms on 2D materials like graphene to exhibit exotic quantum states and correlated phases, driven by van der Waals forces, with implications for future technological applications.

Contribution

It provides a theoretical perspective on how 2D materials can host diverse atomic phases, including supersolids and superfluids, and discusses the tunability and experimental possibilities.

Findings

Helium on 2D materials can form exotic quantum states.

Effective Bose-Hubbard models describe atomic interactions.

Pattern formation at liquid-vapor interface reflects underlying graphene properties.

Abstract

Atoms deposited on two-dimensional (2D) electronic materials, such as graphene, can exhibit unconventional many-body correlations, not accessible in other settings. All of these are driven by van der Waals forces: between the atoms themselves and atom-material interactions. For example $^4$He atoms on 2D materials can potentially form a variety of exotic quantum states of matter, such as two-dimensional supersolids and superfluids, in addition to solid phases. For the "most quantum" case of a single helium layer we discuss, from a theoretical perspective, how the effective low-energy (Bose-Hubbard) description can take advantage of the extreme sensitivity of this unique system to the interplay between the atomic (helium) and solid-state (graphene) components. Due to the extraordinary variety and tunability of 2D electronic materials, we envisage that a wide range of correlated atomic phases can be realized under favorable conditions. We also outline exciting possibilities in the opposite extreme of many atomic layers forming a liquid on top of graphene -- in this case a so-called "spinodal de-wetting" pattern can form at the liquid-vapor interface which reflects the presence and electronic properties of graphene underneath. Such patterns could be manipulated by choosing different atoms and materials, with potential technological applications.