Artificial graphene with tunable interactions

TL;DR

This paper reports the creation of an artificial graphene system using ultracold atoms in a hexagonal optical lattice, exploring the transition from metallic to Mott insulating states with tunable interactions.

Contribution

It introduces a tunable artificial graphene platform with a novel numerical method for Wannier functions and studies the crossover from metallic to Mott insulator regimes.

Findings

Suppression of double occupancy at strong interactions

Observation of a gapped excitation spectrum

Time-resolved equilibration of double occupancy

Abstract

We create an artificial graphene system with tunable interactions and study the crossover from metallic to Mott insulating regimes, both in isolated and coupled two-dimensional honeycomb layers. The artificial graphene consists of a two-component spin mixture of an ultracold atomic Fermi gas loaded into a hexagonal optical lattice. For strong repulsive interactions we observe a suppression of double occupancy and measure a gapped excitation spectrum. We present a quantitative comparison between our measurements and theory, making use of a novel numerical method to obtain Wannier functions for complex lattice structures. Extending our studies to time-resolved measurements, we investigate the equilibration of the double occupancy as a function of lattice loading time.