论文标题
抗铁磁量子自旋三聚体链的分数和复合激发
Fractional and composite excitations of antiferromagnetic quantum spin trimer chains
论文作者
论文摘要
使用量子蒙特卡洛，精确的对角线化和扰动理论，我们通过改变比率$ g = j_2/j_1 $ s = 1/2 $ s = 1/2 $抗磁性Heisenberg Trimer链的光谱。三聚体的双重基础状态形成有效的相互作用$ s = 1/2 $的自由度，由海森堡链描述。因此，当$ g = 1 $时，宽度$ \ propto j_1 $的常规两翼连续体演变为类似的宽度$ \ propto j_2 $当$ g \ to $ g \ to $ g \ 0 $。中型能量和高能量模式称为\ emph {doubleons}和\ emph {Quartons}，它们随着$ g $的增加而形成常规的Spinon Continuum。特别是，在$ g \约0.716 $时，低能旋转旋子分支和带有混合双龙，夸脱顿和纺纱果的高能带之间的差距已关闭。如果可以确定这些特征，则可以在无弹性中子散射实验中观察到，如果可以识别具有线性三聚体结构的准二维量子磁体，并且可以识别$ J_2 <j_1 $。我们的结果可能为探索高能分数激发打开了一个窗口。
Using quantum Monte Carlo, exact diagonalization and perturbation theory, we study the spectrum of the $S=1/2$ antiferromagnetic Heisenberg trimer chain by varying the ratio $g=J_2/J_1$ of the intertrimer and intratrimer coupling strengths. The doublet ground states of trimers form effective interacting $S=1/2$ degrees of freedom described by a Heisenberg chain. Therefore, the conventional two-spinon continuum of width $\propto J_1$ when $g=1$ evolves into to a similar continuum of width $\propto J_2$ when $g\to 0$. The intermediate-energy and high-energy modes are termed \emph{doublons} and \emph{quartons} which fractionalize with increasing $g$ to form the conventional spinon continuum. In particular, at $g \approx 0.716$, the gap between the low-energy spinon branch and the high-energy band with mixed doublons, quartons, and spinons closes. These features should be observable in inelastic neutron scattering experiments if a quasi-one-dimensional quantum magnet with the linear trimer structure and $J_2<J_1$ can be identified. Our results may open a window for exploring the high-energy fractional excitations.
