Jiangyong Yu, Ethan Lauricella, Mohamed Elsayed, Kenneth Shepherd Jr., Nathan S. Nichols, Todd Lombardi, Sang Wook Kim, Carlos Wexler, Juan M. Vanegas, Taras Lakoba, Valeri N. Kotov, and Adrian Del Maestro
An exciting development in the field of correlated systems is the possibility of realizing two-dimensional (2D) phases of quantum matter. For a systems of bosons, an example of strong correlations manifesting themselves in a 2D environment is provided by helium adsorbed on graphene. We construct the effective Bose-Hubbard model for this system which involves hard-core bosons (U=∞), repulsive nearest-neighbor (V>0) and small attractive (V'<0) next-nearest neighbor interactions. The mapping onto the Bose-Hubbard model is accomplished by a variety of many-body techniques which take into account the strong He-He correlations on the scale of the graphene lattice spacing. Unlike the case of dilute ultracold atoms, where interactions are effectively point-like, the detailed microsocpic form of the short range electrostatic and long range dispersion interactions in the helium-graphene system are crucial for the emergent Bose-Hubbard description. The result places the ground state of the first layer of 4He adsorbed on graphene deep in the commensurate solid phase with 1/3 of the sites on the dual triangular lattice occupied. Because the parameters of the effective Bose-Hubbard model are very sensitive to the exact lattice structure, this opens up an avenue to tune quantum phase transitions in this solid-state system.
This repository includes information, code, scripts, and data to generate the figures in a paper.
The raw data in this project was generated via the various methods described in the text. This includes quantum Monte Carlo, density functional theory, etc. To regenerate all quantum Monte Carlo data from scratch, information on obtaining the source code can be found here.
- QMC Data:
The minimal set of reduced data needed to reproduce the figures included in the manuscript is included as a compressed file in data/QMC.tar.bz2 which should expand into a QMC directory. You should set an environment variable HeGrapheneData that provides an absolute path to this directory.
This work was supported, in part, under NASA grant number 80NSSC19M0143. Computational resources were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center.
