Anharmonic ground state selection in the pyrochlore antiferromagnet
Anharmonic ground state selection in the pyrochlore antiferromagnet
复制标题
烧绿石反铁磁体中的非谐基态选择
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
C. Henley
中科院分区：
文献类型：
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作者：
U. Hizi;C. Henley
在焦绿石晶格Heisenberg反铁磁体中，对于大自旋长度$S$，自旋波中谐波阶量子涨落的零点能量部分解除了大量经典基态简并。然而，仍然存在一个无限流形的简并共线基态，由一个规范对称联系起来。我们已经将自旋波计算扩展到四次阶，假设一个高斯变分波函数（相当于Hartree-Fock近似）。四次计算确实打破了周期基态的谐波阶简并。描述这种依赖于回路的分裂的有效哈密顿量的形式，被数值拟合并被解析合理化。我们发现一组状态几乎仍然是简并的，被长度为26的循环项所分割。我们还计算了棋盘格的非调和项，并讨论了为什么它（以及kagom'e晶格）在非调和阶上与焦绿石的行为不同。
In the pyrochlore lattice Heisenberg antiferromagnet, for large spin length $S$, the massive classical ground state degeneracy is partly lifted by the zero-point energy of quantum fluctuations at harmonic order in spin waves. However, there remains an infinite manifold of degenerate collinear ground states, related by a gaugelike symmetry. We have extended the spin-wave calculation to quartic order, assuming a Gaussian variational wave function (equivalent to Hartree-Fock approximation). Quartic calculations do break the harmonic-order degeneracy of periodic ground states. The form of the effective Hamiltonian describing this splitting, which depends on loops, was fitted numerically and also rationalized analytically. We find a family of states that are still almost degenerate, being split by the term from loops of length 26. We also calculated the anharmonic terms for the checkerboard lattice, and discuss why it (as well as the kagom'e lattice) behave differently than the pyrochlore at anharmonic orders.