Title | Proximity effects in cold atom artificial graphene |
Publication Type | Journal Article |
Year of Publication | 2016 |
Authors | T. Grass, R. W. Chhajlany, L. Tarruell, V. Pellegrini, and M. Lewenstein |
Journal | 2D Materials |
Volume | 4 |
Issue | 1 |
Date Published | 12/2016 |
Abstract | Cold atoms in an optical lattice with brick-wall geometry have been used to mimic graphene, a two-dimensional material with characteristic Dirac excitations. Here we propose to bring such artificial graphene into the proximity of a second atomic layer with a square lattice geometry. For non-interacting fermions, we find that such bilayer system undergoes a phase transition from a graphene-like semi-metal phase, characterized by a band structure with Dirac points, to a gapped band insulator phase. In the presence of attractive interactions between fermions with pseudospin-1/2 degree of freedom, a competition between semi-metal and superfluid behavior is found at the mean-field level. Using the quantum Monte Carlo method, we also investigate the case of strong repulsive interactions. In the Mott phase, each layer exhibits a different amount of long-range magnetic order. Upon coupling both layers, a valence-bond crystal is formed at a critical coupling strength. Finally, we discuss how these bilayer systems could be realized in existing cold atom experiments. |
URL | http://iopscience.iop.org/article/10.1088/2053-1583/aa50c6/meta;jsessionid=D34C5DE028C6A9A2A9B6D6A0A65569AF.c2.iopscience.cld.iop.org |
DOI | 10.1088/2053-1583/aa50c6 |