论文标题
$ s = 1/2 $ $ j_1 $ - $ j_2 $ square-kagome晶格抗fiferromagnet的磁性
Magnetism of the $s=1/2$ $J_1$-$J_2$ square-kagome lattice antiferromagnet
论文作者
论文摘要
Square-Kagome（SK）晶格上的旋转$ 1/2 $ Heisenberg Antiferromagnet吸引了人们越来越多的关注，因为它是一种高度沮丧的量子磁性模型系统。理论研究的进一步动机来自最近发现SK旋转化合物。 SK AntiferRomagnet展示了两个非等效的最近的邻居债券$ J_1 $和$ J_2 $。人们可能会期望在SK化合物中$ J_1 $和$ J_2 $具有不同的强度。我们通过有限温度的lanczos方法对有限系统进行了数值研究。 We discuss the temperature dependence of the specific heat $C(T)$, the entropy $S(T)$, and of the susceptibility $X(T)$ of the $J_1$-$J_2$ SK Heisenberg antiferromagnet varying $J_2/J_1$ in the range $0 \le J_2/J_1 \le 4$.我们还讨论了模型的零视野基态。我们发现磁性无序的单线基态的适应症，价格为$ 0 \ le J_2/J_1 \ Lessim 1.65 $。超过$ j_2/j_1 \ sim 1.65 $ singlet基态为铁磁基态而取代。在该区域中，$ 0.77 \ Lessim J_2/J_1 \ Lessim 1.65 $低温热力学以有限的单重手柄间隙为主导，充满了低俗的单线激励，导致指数激活的低温行为$ x（t）$。另一方面，低洼的单元在$ c（t）$曲线的主要最大值以下产生额外的最大值或类似肩膀的轮廓。对于$ J_2/J_1 \ Lessim 0.7 $，低温热力学的特征是$ n/3 $的很大一部分均为弱耦合的旋转，导致在非常低温下的大量熵。在应用的磁场中，磁化过程具有高原和跳跃$ j_2/j_1 $的范围。
The spin-$1/2$ Heisenberg antiferromagnet on the square-kagome (SK) lattice has attracted growing attention as a model system of highly frustrated quantum magnetism. A further motivation for theoretical studies comes from the recent discovery of SK spin-liquid compounds. The SK antiferromagnet exhibits two non-equivalent nearest-neighbor bonds $J_1$ and $J_2$. One may expect that in SK compounds $J_1$ and $J_2$ are of different strength. We present a numerical study of finite systems by means of the finite-temperature Lanczos method. We discuss the temperature dependence of the specific heat $C(T)$, the entropy $S(T)$, and of the susceptibility $X(T)$ of the $J_1$-$J_2$ SK Heisenberg antiferromagnet varying $J_2/J_1$ in the range $0 \le J_2/J_1 \le 4$. We also discuss the zero-field ground state of the model. We find indications for a magnetically disordered singlet ground state for $0 \le J_2/J_1 \lesssim 1.65$. Beyond $J_2/J_1 \sim 1.65$ the singlet ground state gives way for a ferrimagnetic ground state. In the region $0.77 \lesssim J_2/J_1 \lesssim 1.65$ the low-temperature thermodynamics is dominated by a finite singlet-triplet gap filled with low-lying singlet excitations leading to an exponentially activated low-temperature behavior of $X(T)$. On the other hand, the low-lying singlets yield an extra maximum or a shoulder-like profile below the main maximum in the $C(T)$ curve. For $J_2/J_1 \lesssim 0.7$ the low-temperature thermodynamics is characterized by a large fraction of $N/3$ weakly coupled spins leading to a sizable amount of entropy at very low temperatures. In an applied magnetic field the magnetization process features plateaus and jumps in a wide range of $J_2/J_1$.
