层状横波光学声子的非简谐性对高温超导电性的影响

本文采用二能级(TLS)模型,利用正则变换方法,研究氧化物超导体中层状横波光学声子的非简谐性对层间配对的影响,结果表明:只有在二能级差Ω小于临界值Ω_c时,T_c才不为零;Ω越小,T_c越大,这与实验中所显示的绝缘层离子的轴向运动的重要性是一致的。 关键词：     

Particle-hole bound states of dipolar molecules in an optical lattice

We investigate the particle-hole pair excitations of dipolar molecules in an optical lattice, which can be described with an extended Bose-Hubbard model. For strong enough dipole-dipole interaction, the particle-hole pair excitations can form bound states in one and two dimensions. With decreasing dipole-dipole interaction, the energies of the bound states increase and merge into the particle-hole continuous spectrum gradually. The existence regions, the energy spectra and the wave functions of the bound states are carefully studied and the symmetries of the bound states are analyzed with group theory. For a given dipole-dipole interaction, the number of bound states varies in momentum space and a number distribution of the bound states is illustrated. We also discuss how to observe these bound states in future experiments.     

双层Heisenberg反铁磁体中的量子相变

用键算符平均场方法研究了双层正方格子Heisenberg反铁磁体中的量子相变问题.得到的临界点以及低温下的量子临界行为符合相关的数值计算结果和非线性σ模型的结果.在数值计算不能达到的极低温度范围（T≤0.3J₁,J₁为面内最近邻反铁磁交换作用）,给出了量子临界行为的新证据. 关键词：