We study the topological properties of Bogoliubov excitation modes in a Bose–Hubbard model of three-dimensional(3 D)hyperhoneycomb lattices.For the non-interacting case,there exist nodal loop excitations in the Bloch...We study the topological properties of Bogoliubov excitation modes in a Bose–Hubbard model of three-dimensional(3 D)hyperhoneycomb lattices.For the non-interacting case,there exist nodal loop excitations in the Bloch bands.As the on-site repulsive interaction increases,the system is first driven into the superfluid phase and then into the Mott-insulator phase.In both phases,the excitation bands exhibit robust nodal-loop structures and bosonic surface states.From a topology point of view,these nodal-loop excitation modes may be viewed as a permanent fingerprint left in the Bloch bands.展开更多
The symmetric and the asymmetric double-chain Bose-Hubbard Models( BHMs) are studied by the mean-field theory. By using Landau's quantum phase transition theory,phase diagrams for systems with different hopping en...The symmetric and the asymmetric double-chain Bose-Hubbard Models( BHMs) are studied by the mean-field theory. By using Landau's quantum phase transition theory,phase diagrams for systems with different hopping energies and repulsive interactions are obtained. Thereby,Mott-insulator-superfluid( MISF)phase transition boundaries are determined. Our results show that tunneling effects between two chains provide additional channels for particles hopping between corresponding optical lattice sites of different chains,which makes easier for systems to transit from MI to SF phase. The two-site parity function is also utilized to investigate the properties of the system near the quantum phase transit point.We found that the increase of inter-chain hopping will reinforce the tunneling effects between two chains,and reduce the intrachain tunneling effects within the same chain.展开更多
The phase diagram of the one-dimensional Bose-Hubbard model describing interacting bosons in optical lattice is investigated with the variational approach. This method can also be generalized to the two-dimensional case.
Critical temperature and condensate fraction of Bose-Einstein condensation in the optical lattice are studied. The results show that the critical temperature in optical lattices can be characterized with an equivalent...Critical temperature and condensate fraction of Bose-Einstein condensation in the optical lattice are studied. The results show that the critical temperature in optical lattices can be characterized with an equivalent critical temperature in a single lattice, which provide a fast evaluation of critical temperature and condensate fraction of Bose-Einstein condensation confined with pure optical trap. Critical temperature can be estimated with an equivalent critical temperature. It is predicted that critical temperature is proportional to q ?3/2 in q number lattices for superfluid state and should be equal to that in a single lattic for Mott insulate state. Required potential depth or Rabi frequency and maximum atom number in the lattices both for superfluid state and Mott state are presented based on views of thermal mechanical statistics.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474025,11674026,and 11504285)Specialized Research Fund for the Doctoral Program,ChinaYoung Talent Fund of University Association for Science and Technology in Shaanxi,China(Grant No.20160224)
文摘We study the topological properties of Bogoliubov excitation modes in a Bose–Hubbard model of three-dimensional(3 D)hyperhoneycomb lattices.For the non-interacting case,there exist nodal loop excitations in the Bloch bands.As the on-site repulsive interaction increases,the system is first driven into the superfluid phase and then into the Mott-insulator phase.In both phases,the excitation bands exhibit robust nodal-loop structures and bosonic surface states.From a topology point of view,these nodal-loop excitation modes may be viewed as a permanent fingerprint left in the Bloch bands.
基金Sponsored by the National Natural Science Foundation China(Grant No.11504106)the Special Foundation for Theoretical Physics Research Program of China(Grant No.11447167)
文摘The symmetric and the asymmetric double-chain Bose-Hubbard Models( BHMs) are studied by the mean-field theory. By using Landau's quantum phase transition theory,phase diagrams for systems with different hopping energies and repulsive interactions are obtained. Thereby,Mott-insulator-superfluid( MISF)phase transition boundaries are determined. Our results show that tunneling effects between two chains provide additional channels for particles hopping between corresponding optical lattice sites of different chains,which makes easier for systems to transit from MI to SF phase. The two-site parity function is also utilized to investigate the properties of the system near the quantum phase transit point.We found that the increase of inter-chain hopping will reinforce the tunneling effects between two chains,and reduce the intrachain tunneling effects within the same chain.
文摘The phase diagram of the one-dimensional Bose-Hubbard model describing interacting bosons in optical lattice is investigated with the variational approach. This method can also be generalized to the two-dimensional case.
文摘Critical temperature and condensate fraction of Bose-Einstein condensation in the optical lattice are studied. The results show that the critical temperature in optical lattices can be characterized with an equivalent critical temperature in a single lattice, which provide a fast evaluation of critical temperature and condensate fraction of Bose-Einstein condensation confined with pure optical trap. Critical temperature can be estimated with an equivalent critical temperature. It is predicted that critical temperature is proportional to q ?3/2 in q number lattices for superfluid state and should be equal to that in a single lattic for Mott insulate state. Required potential depth or Rabi frequency and maximum atom number in the lattices both for superfluid state and Mott state are presented based on views of thermal mechanical statistics.
