期刊
2D MATERIALS
卷 4, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/2053-1583/aa50c6
关键词
cold atoms in optical lattices; artificial graphene; superfluidity; proximity effect
资金
- European Union [339106 OSYRIS, FP7-ICT-2011-9, 600645 SIQS, H2020-FETPROACT-2014, 641122 QUIC, 323714 Equam, PCIG13-GA-2013, 631633 Mag-QUPT]
- Spanish MINECO [FIS2013-46768-P FOQUS, FIS2014-59546-P StrongQSIM, SEV-2015-0522 Severo Ochoa]
- Generalitat de Catalunya [2014 SGR 874]
- German DFG [FOR 2414]
- AFOSR-MURI
- Fundacio Cellex
- KITPC Program 'Spin-orbit-coupled quantum gases'
- ICREA Funding Source: Custom
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.
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