论文标题
pyrochlore s = 1/2在有限温度下Heisenberg Antiferromagnet
The pyrochlore S=1/2 Heisenberg antiferromagnet at finite temperature
论文作者
论文摘要
众所周知，沮丧的三维量子磁铁对理论分析不透气。在这里，我们使用三种计算方法的组合来研究三维的pyrochlore $ s = 1/2 $量子防fiferromagnet，一种典型的挫折磁铁，在有限温度下，$ t $：适用于$ 2 \ times $ 2 \ timess 2 \ times $ 32 $ 32 $ 32 $ 32 $ 32 $ 32 $ 32 $ 32 $ 32 $ 32 $ 32的有限群集的规范典型性， $ 48 $站点，以及使用高达$ 25 $晶格网站的群集的数值链接群集扩展（NLCE），其中包括非平凡的六角形和八角形循环。我们关注静态结构因子旁边的热力学特性（能量，特定的热容量，熵，易感性，磁化）。我们在$ t = 0.57 j $的特定热量中发现了一个明显的最大值，在有限尺寸簇中稳定，并且在系列扩展中融合。这与剩余的频谱重量为0.47 k_b \ ln 2 $的剩余量，即使在$ t \ of约0.25 j $，这是我们结果的收敛极限。与许多高度沮丧的模型和材料（例如旋转冰或Kagome $ s = 1/2 $ heisenberg antiferromagnet）相比，这是一个很大的价值。我们还发现在低磁场处磁化的$ t $的非单调依赖性，反映了低能量光谱重量的主要非磁性特征。我们的结果与$ s = 1 $材料nacani $ _2 $ f $ _7 $的详细比较，对特定热量的功能形式进行了粗略的一致性，这反过来又不同于旋转冰材料的热量最大值$ _2 $ _2 $ _2 $ _2 $ _2 $ _2 $ o _7 $ _7 $，与所有这些都不同，这是与之差异的。
Frustrated three dimensional quantum magnets are notoriously impervious to theoretical analysis. Here we use a combination of three computational methods to investigate the three dimensional pyrochlore $S=1/2$ quantum antiferromagnet, an archetypical frustrated magnet, at finite temperature, $T$: canonical typicality for a finite cluster of $2\times 2 \times 2$ unit cells (i.e. $32$ sites), a finite-$T$ matrix product state method on a larger cluster with $48$ sites, and the numerical linked cluster expansion (NLCE) using clusters up to $25$ lattice sites, which include non-trivial hexagonal and octagonal loops. We focus on thermodynamic properties (energy, specific heat capacity, entropy, susceptibility, magnetisation) next to the static structure factor. We find a pronounced maximum in the specific heat at $T = 0.57 J$, which is stable across finite size clusters and converged in the series expansion. This is well-separated from a residual amount of spectral weight of $0.47 k_B \ln 2$ per spin which has not been released even at $T\approx0.25 J$, the limit of convergence of our results. This is a large value compared to a number of highly frustrated models and materials, such as spin ice or the kagome $S=1/2$ Heisenberg antiferromagnet. We also find a non-monotonic dependence on $T$ of the magnetisation at low magnetic fields, reflecting the dominantly non-magnetic character of the low-energy spectral weight. A detailed comparison of our results to measurements for the $S=1$ material NaCaNi$_2$F$_7$ yields rough agreement of the functional form of the specific heat maximum, which in turn differs from the sharper maximum of the heat capacity of the spin ice material Dy$_2$Ti$_2$O$_7$, all of which are yet qualitatively distinct from conventional, unfrustrated magnets.
