欠屏蔽近藤晶格的规范平均场理论

中文摘要 AI 辅助

迄今为止，人们引入了各种平均场解耦方案来研究自旋为$1$的欠屏蔽近藤晶格这一重要且具有挑战性的问题，其中磁序可以与近藤杂化共存。我们使用单一控制参数$N$和一个无偏变分拟设，将先前提出的解耦方案统一并联系到标准的Read-Newns理论，在该理论中，$1/N$阶的涨落很小。我们计算了大$N$极限周围的修正。特别是，我们通过找到在重费米子金属情形下对数衰减的残余铁磁Hund相互作用，与Nozières强耦合理论建立了联系。我们绘制了作为$N$和近藤耦合函数的基态相图。我们发现先前提出的平均场理论在杂化强度和共存相的总磁化强度方面存在关键差异。我们表明，在我们统一的变分理论中，先前提出的解耦方案对应于要么从一开始就取$N=2$，要么进行$1/N$展开然后外推到$N=2$。最后，我们总结了我们的理论对$S>1$情形的推广。

英文摘要

Various mean-field decoupling schemes have been introduced thus far to study the important and challenging problem of the spin-$1$ underscreened Kondo lattice where magnetic order can coexist with Kondo hybridization. We use a single control parameter $N$ and an unbiased variational ansatz to unify and connect the previously proposed decouplings to standard Read-Newns theory, where fluctuations are small in $1/N$. We compute the corrections around the large-$N$ limit. In particular, we make contact with Nozières strong-coupling theory by finding the residual ferromagnetic Hund interaction that decays logarithmically in the case of a heavy-fermion metal. We map out the ground state phase diagram as a function of $N$ and the Kondo coupling. We find crucial differences between the previously proposed mean-field theories in the strength of the hybridization and total magnetization of the coexistent phase. We show that, within our unifying variational theory, the previously proposed decouplings correspond to either taking $N=2$ from the start, or performing a $1/N$ expansion and then extrapolating to $N=2$. Finally, we summarize the generalization of our theory to $S>1$.

发表机构

• University College London（伦敦大学学院）
• Trinity College, Cambridge（剑桥大学三一学院）

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