论文标题
量子自旋链中的无间隙至无间隙相变
Gapless to gapless phase transitions in quantum spin chains
论文作者
论文摘要
我们研究了双线性 - 骨化链（BLBQ）旋转相互作用的旋转链，这是应用磁场$ h $的函数。在Uimin-Lai-Sutherland（ULS）临界点，我们发现动态结构因子$ s（Q，ω）$的无间隙转换是$ h $的函数。在$ h = 0 $时，最低能量激发的信封在{\ it两个点} $ q_1 =2π/3 $和$ q_2 =4π/3 $时变为A相位。随着磁场的增加，光谱峰在每个范围内的光谱峰，在每个无间隙点上的bifurcate上，总计{\ IT {\ IT四个软模式都可以启动，并组合成型，并组合组合，组合组合组合，并组合组合组合。 {\ it单}点$ q =π$在$ h_ {c1} \大约0.94 $。超过$ h_ {c1} $该系统进入另一个无间隙B相，直到以$ h_ {c2} = 4 $的过渡到完全极化阶段。我们将ULS模型的结果与AKLT模型的结果进行比较，作为Gapped Haldane相位的代表。我们使用其保守的电荷和Spinon频段图片来解释ULS模型中无间隙转换的机制。我们还讨论了经受磁场的BLBQ模型家族的中心电荷的通用性。
We investigate spin chains with bilinear-biquadratic (BLBQ) spin interactions as a function of an applied magnetic field $h$. At the Uimin-Lai-Sutherland (ULS) critical point we find a gapless to gapless transition revealed by the dynamical structure factor $S(q,ω)$ as a function of $h$. At $h=0$, the envelope of the lowest energy excitations goes soft at {\it two points} $q_1=2π/3$ and $q_2=4π/3$, dubbed the phase A. With increasing field, the spectral peaks at each of the gapless points bifurcate, making in total {\it four} soft modes, and combine to form a new set of excitations that soften at a {\it single} point $q=π$ at $h_{c1}\approx 0.94$. Beyond $h_{c1}$ the system enters another gapless B-phase until the transition at $h_{c2}=4$ to the fully polarized phase. We compare the ULS model results with those for the AKLT model as a representative of gapped Haldane phase. We explain the mechanism of the gapless to gapless transition in the ULS model using its conserved charges and a spinon band picture. We also discuss the universality of central charges of the BLBQ family of models subjected to a magnetic field.
