Variational study of the ground state and spin dynamics of the spin-1/2 kagome antiferromagnetic Heisenberg model and its implication for herbertsmithite ZnCu3(OH)(6)Cl-2
Variational study of the ground state and spin dynamics of the spin-1/2 kagome antiferromagnetic Heisenberg model and its implication for herbertsmithite ZnCu3(OH)(6)Cl-2
复制标题
自旋1/2 kagome反铁磁海森堡模型基态和自旋动力学的变分研究及其对镁铁矿ZnCu3(OH)(6)Cl-2的影响
DOI：
10.1103/physrevb.102.195106
复制
发表时间：
2020
影响因子：
3.7
通讯作者：
Li Tao
中科院分区：
文献类型：
--
作者：
Zhang Chun;Li Tao
我们发现，自旋-Kagome反铁磁海森堡模型（spin-KAFH）的最佳共振价键（RVB）态是由属于这类的平均场色散描述的，它具有与广泛研究的Dirac自旋液体态非常不同的平均场自旋色散.然而，我们发现，在这样的RVB态上，由Gutzwiller投影无规相位近似（RPA）（GRPA）理论计算的物理自旋涨落谱实际上是无带隙的，并且与Dirac自旋液体态上的物理自旋涨落谱几乎相同。我们发现，这种特殊的行为可以归因于kagome晶格上独特的平带物理，它使得平均场与RVB态之间的映射是非内射的。我们发现自旋KAFH的自旋涨落谱并非毫无特征，而是在~附近有一个显著的谱峰，它处于~的宽连续区中。在此基础上，我们认为，在赫伯氏体中子非弹性散射谱中，2 meV以下的谱峰是由占据赫伯氏体的杂质自旋的贡献引起的，而应理解为来自kagome层的本征贡献。我们建议通过测量Cu位而不是O位上的奈特位移来验证这样的图像，由于戈薇晶格上最近相邻自旋之间的强反铁磁相关性，O位几乎对该点的自旋波动一无所知。
We find that the best resonating valence bond (RVB) state of the spin-kagome antiferromagnetic Heisenberg model (spin-KAFH) is described by amean field ansatz belonging to theclass, which hosts a mean field spinon dispersion very different from that of the widely studiedDirac spin liquid state. However, we find that the physical spin fluctuation spectrum calculated from the Gutzwiller projected random phase approximation (RPA) (GRPA) theory above such an RVB state is actually gapless and is almost identical to that above theDirac spin liquid state. We find that such a peculiar behavior can be attributed to the unique flat band physics on the kagome lattice, which makes the mapping between the mean field ansatz and the RVB state noninjective. We find that the spin fluctuation spectrum of the spin-KAFH is not at all featureless, but is characterized by a prominent spectral peak at aboutaround thepoint, which is immersed in a broad continuum extending to. Based on these results, we argue that the spectral peak below 2 meV in the inelastic neutron scattering spectrum of hebertsmithite, which has been attributed to the contribution ofimpurity spins occupying thesite, should rather be understood as the intrinsic contribution from the kagome layer. We propose to verify such a picture by measuring the Knight shift on the Cu site, rather than the O site, which is almost blind to the spin fluctuation at thepoint as a result of the strong antiferromagnetic correlation between nearest neighboring spins on the kagome lattice.