Quantum and classical spins on the spatially distorted kagomé lattice: Applications to volborthiteCu3V2O7(OH)2∙2H2O
Quantum and classical spins on the spatially distorted kagomé lattice: Applications to volborthiteCu3V2O7(OH)2∙2H2O
复制标题
空间扭曲 Kagomé 晶格上的量子和经典自旋：在 volborthiteCu3V2O7(OH)2∙2H2O 中的应用
DOI：
10.1103/physrevb.76.094421
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发表时间：
2007
影响因子：
3.7
通讯作者：
Yong Baek Kim
中科院分区：
文献类型：
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作者：
Fa Wang;A. Vishwanath;Yong Baek Kim
在Volborthite中，自旋-1/2力矩形成了一个扭曲的Kagom\'e晶格，由两个键的交换常数为$J$和第三个键的交换常数为$J'$的角共享等腰三角形组成。我们研究了这种自旋系统的性质，并表明尽管存在畸变，晶格仍然保留了大量的挫折。虽然是次扩展的，但经典基态简并仍然非常大，随系统周长呈指数增长。我们考虑由热涨落和量子涨落引起的简并提升。对于线性（自旋波）阶，简并性保持不变。因此，引入了两种互补的方法，适用于低温和高温，它们指向相同的有序模式。在低温极限下，从非线性自旋波中导出了有效手性哈密顿量，并预测了增加$J′/J$时，从$\sqrt 3\乘以\sqrt 3$型阶向具有双单元胞的新铁磁{\em条纹手性}阶的转变。这可以通过在这个晶格上的O（$n$）模型上的大n近似得到证实。当鞍点解产生直线简并时，$O(1/n)$修正选择条纹手性态的非平凡波向量。通过精确的小系统对角化研究了该晶格上自旋1/2的量子极限，并与实验结果在中温下进行了比较。我们认为在核磁共振实验中看到的极低温自旋冻结状态可能与该晶格上经典基态的断开性有关，这导致了对核磁共振线形状的预测。
In Volborthite, spin-1/2 moments form a distorted Kagom\'e lattice, of corner sharing isosceles triangles with exchange constants $J$ on two bonds and $J'$ on the third bond. We study the properties of such spin systems, and show that despite the distortion, the lattice retains a great deal of frustration. Although sub-extensive, the classical ground state degeneracy remains very large, growing exponentially with the system perimeter. We consider degeneracy lifting by thermal and quantum fluctuations. To linear (spin wave) order, the degeneracy is found to stay intact. Two complementary approaches are therefore introduced, appropriate to low and high temperatures, which point to the same ordered pattern. In the low temperature limit, an effective chirality Hamiltonian is derived from non-linear spin waves which predicts a transition on increasing $J'/J$, from $\sqrt 3\times \sqrt 3$ type order to a new ferrimagnetic {\em striped chirality} order with a doubled unit cell. This is confirmed by a large-N approximation on the O($n$) model on this lattice. While the saddle point solution produces a line degeneracy, $O(1/n)$ corrections select the non-trivial wavevector of the striped chirality state. The quantum limit of spin 1/2 on this lattice is studied via exact small system diagonalization and compare well with experimental results at intermediate temperatures. We suggest that the very low temperature spin frozen state seen in NMR experiments may be related to the disconnected nature of classical ground states on this lattice, which leads to a prediction for NMR line shapes.
ALPS Project-量子晶格模型开源软件-
DOI：
--
发表时间：
2008
期刊：
影响因子：
--
作者：
H.Orihara;T.Shibuya;T.Nagaya;S.Ujiie;藤堂眞治
通讯作者：
藤堂眞治