Atomically thin superfluid and solid phases for atoms on strained graphene

Atoms deposited on atomically thin substrates are a playground for exotic quantum many-body physics due to the highly tunable, atomic-scale nature of the interaction potentials. The ability to engineer strong interparticle interactions can lead to the emergence of collective states of matter, not possible in the context of dilute atomic gases confined in optical lattices. While it is known that the first layer of adsorbed helium on graphene is permanently locked into a solid phase, we motivate, with a physically intuitive mean-field calculation, and confirm, with quantum Monte Carlo simulations, that simple isotropic graphene lattice expansion unlocks a large variety of two-dimensional ordered commensurate, incommensurate, cluster atomic solid, and superfluid states for adsorbed atoms. It is especially significant that an atomically thin superfluid phase of matter emerges under experimentally feasible strain values, with potentially supersolid phases in close proximity on the phase diagram.