论文标题
旋转中的订单,混乱和单极限制 - $ 1/2 $ xxz型号在Pyrochlore管上
Order, Disorder and Monopole Confinement in the Spin-$1/2$ XXZ Model on a Pyrochlore Tube
论文作者
论文摘要
我们研究了Spin-Half XXZ模型的基态和热力学特性,该模型具有ISING相互作用$ J_Z $和横向交换相互作用$ J_ {X} $,这是通过在一维阵列中加入基本立方体获得的pyrochlore管。横向方向的周期性边界条件可确保系统的大部分由角共享的四面体组成,四面体和局部几何形状与pyrochlore晶格相同。我们使用精确的对角度化,密度矩阵重新归一化组(DMRG)以及最小纠缠的典型热状态(METTS)方法来研究该系统。当$ j_z $是抗fiferromagnetic($ j_ {z}> 0 $),而$ j_x $是ferromagnetic($ j_ {x} <0 $)时,我们发现从旋转液体过渡到XY Ferromagnet,其幂律相关性为$ t = 0 $。对于$ j_ {z} <0 $和$ j_ {x}> 0 $,发现旋转两种激发的能量低于远离完全极化状态的旋转型,从而显示出了刚开始的自旋循环序列的证据。当两种相互作用都是抗铁磁磁性时,我们发现一个非分类基态,没有断裂的对称性和牢固的能量隙。低能光谱从主要属于XY相互作用的主要分析中平稳地发展。在小$ | j_ {x} | $的自旋液体状态中,我们研究了单翼 - 抗单键孔对的限制,发现限制长度比例比$ j_x <0 $要大于$ j_ {x}> 0 $,尽管两个长度比例都很短。这些结果与海森堡抗铁磁铁的局部自旋液相一致,没有断裂的对称性。
We study the ground state and thermodynamic properties of the spin-half XXZ model, with an Ising interaction $J_z$ and a transverse exchange interaction $J_{x}$, on a pyrochlore tube obtained by joining together elementary cubes in a one-dimensional array. Periodic boundary conditions in the transverse directions ensure that the bulk of the system consists of corner-sharing tetrahedra, with the same local geometry as the pyrochlore lattice. We use exact diagonalization, the density matrix renormalization group (DMRG), and minimally entangled typical thermal states (METTS) methods to study the system. When $J_z$ is antiferromagnetic ($J_{z}>0$) and $J_x$ is ferromagnetic ($J_{x}<0$), we find a transition from a spin liquid to an XY ferromagnet, which has power-law correlations at $T=0$. For $J_{z}<0$ and $J_{x}>0$, spin-two excitations are found to have lower energy than spin-one at the transition away from the fully polarized state, showing evidence for incipient spin-nematic order. When both interactions are antiferromagnetic, we find a non-degenerate ground state with no broken symmetries and a robust energy gap. The low energy spectra evolve smoothly from predominantly Ising to predominantly XY interactions. In the spin-liquid regime of small $|J_{x}|$, we study the confinement of monopole-anti-monopole pairs and find that the confinement length scale is larger for $J_x<0$ than for $J_{x}>0$, although both length scales are very short. These results are consistent with a local spin-liquid phase for the Heisenberg antiferromagnet with no broken symmetries.