具有Dzyaloshinskii-Moriya相互作用的XY模型的量子相干性

研究了具有Dzyaloshinskii-Moriya(DM)相互作用的一维横场XY自旋链的量子相变和量子相干性.采用约旦-维格纳变换严格求解了哈密顿量,并描绘了体系的关联函数和相图,相图包含反铁磁相、顺磁相和螺旋相.利用相对熵和Jensen-Shannon熵讨论了XY模型的量子相干性.研究发现,相对熵与Jensen-Shannon熵所表现的行为都可以很好地表征该模型的量子相变.非螺旋相中量子相干性不依赖DM相互作用,而在螺旋相DM相互作用对量子相干性有显著影响.此外,指出了在带有DM相互作用的这一类反射对称破缺体系中关联函数计算的常见问题.     

带有三体相互作用的S=1自旋链中的保真率和纠缠熵

研究了带有次近邻和三体相互作用的S=1自旋链的保真率和纠缠熵.通过密度矩阵重整化群数值方法计算了三体相互作用对保真率的影响,并分析了其与量子相变的关系.研究表明保真率可以探测Haldane相与二聚物相之间的相变.此外还研究了该相变与量子纠缠熵的关系.通过保真率和量子纠缠熵这两个信息观测量得到的结果和弦序参量得到的结果一致.在此基础之上给出了相图.     

Competitions of magnetism and superconductivity in FeAs-based materials

Using the numerical unrestricted Hartree--Fock approach, we study the ground state of a two-orbital model describing newly discovered FeAs-based superconductors. We observe the competition of a (0, π) mode spin-density wave and the superconductivity as the doping concentration changes. There might be a small region in the electron-doping side where the magnetism and superconductivity coexist. The superconducting pairing is found to be spin singlet, orbital even, and coexisting s_xy + d_x²-y² wave (even parity).     

由杂质自旋散射引起的纠缠

研究了自由电子与固定杂质自旋的散射过程中的纠缠行为.研究发现,固定自旋的杂质能起到纠缠过滤器的作用,实现自由电子间的纠缠浓缩.当两无相互作用的电子先后经过同一Kondo杂质并与之发生散射时,可以使得原本不纠缠的电子发生纠缠.类似地,当运动的电子先后经过两无相互作用的Kondo杂质并与它们发生散射,可以使得原本不纠缠的K...     

Two-dimensional quantum compass model in a staggered field: some rigorous results

We study the properties of the two-dimensional quantum compass model in a staggered field. Using the Perron--Fröbenius theorem and the reflection positivity method, we rigorously determine the low energy spectrum of this model and its global ground state Ψ₀. Furthermore, we show that Ψ₀ has a directional long-range order.