In this paper we investigate classical and quantum phase transitions of Bose-Hubbard model in checkerboard superlattices with a magnetic field at the mean-field level. By analyzing stability of normal state phase boun...In this paper we investigate classical and quantum phase transitions of Bose-Hubbard model in checkerboard superlattices with a magnetic field at the mean-field level. By analyzing stability of normal state phase boundaries are obtained analytically for zero and finite temperature in a unified theoretical frame and easily extended to the situation without the magnetic field. All results illustrate that the introduction of the magnetic field enhances the stability of normal state and Mort insulator. In addition we also note that the critical hopping term presents an oscillating behavior inversely following the upper boundary of Hofstadter butterfly.展开更多
A transverse Ising spin system, in the presence of time-dependent longitudinal field, is studied by the effective-field theory （EFT）. The effective-field equations of motion of the average magnetization are given fo...A transverse Ising spin system, in the presence of time-dependent longitudinal field, is studied by the effective-field theory （EFT）. The effective-field equations of motion of the average magnetization are given for the simple cubic lattice （Z ---- 6） and the honeycomb lattice （Z = 3）. The Liapunov exponent A is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. The dynamic phase transition diagrams in ho/ZJ - F/ZJ plane and in ho/ZJ - T/ZJ plane have been drawn, and there is no dynamical tricritical point on the dynamic phase transition boundary. The effect of the thermal fluctuations upon the dynamic phase boundary has been discussed.展开更多
基金Supported by National Natural Science Foundation of China under Grant No.10675108Foundation of Yancheng Institute of Technology under Grant No.XKR2010007
文摘In this paper we investigate classical and quantum phase transitions of Bose-Hubbard model in checkerboard superlattices with a magnetic field at the mean-field level. By analyzing stability of normal state phase boundaries are obtained analytically for zero and finite temperature in a unified theoretical frame and easily extended to the situation without the magnetic field. All results illustrate that the introduction of the magnetic field enhances the stability of normal state and Mort insulator. In addition we also note that the critical hopping term presents an oscillating behavior inversely following the upper boundary of Hofstadter butterfly.
文摘A transverse Ising spin system, in the presence of time-dependent longitudinal field, is studied by the effective-field theory （EFT）. The effective-field equations of motion of the average magnetization are given for the simple cubic lattice （Z ---- 6） and the honeycomb lattice （Z = 3）. The Liapunov exponent A is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. The dynamic phase transition diagrams in ho/ZJ - F/ZJ plane and in ho/ZJ - T/ZJ plane have been drawn, and there is no dynamical tricritical point on the dynamic phase transition boundary. The effect of the thermal fluctuations upon the dynamic phase boundary has been discussed.
