论文标题
$ r \ mathrm {b} _ {12} $中的磁性，量子关键性和金属绝缘体过渡
Magnetism, quantum criticality, and metal-insulator transitions in $R\mathrm{B}_{12}$
论文作者
论文摘要
审查了稀土（RE）DodeCaborides的物理特性，其特征在于具有松散结合的离子的笼玻璃晶体结构。这些化合物是具有同时有效的电荷，旋转，轨道和晶格自由度的强度相关的电子系统，这解释了所有$ r \ mathrm {b} _ {12} $化合物的所有复杂性（lub $ _ {12} $）一侧，以及所谓的昆多绝缘子化合物ybb $ _ {12} $和基于yb的yb $ _ {x} r_ {1-x} r_ {1-x} $ b $ _ {12} $ {12} $实心解决方案。共价硼网络的合作动态jahn-teller不稳定性的发展会产生刚性笼子的三角形和四方畸变，并导致降低了十二焦点中FCC晶格的对称性降低。硼亚晶格中的铁体抗体动力学同时生成了重型离子的集体模式和准局部振动（嘎嘎声模式），从而导致电荷载波密度的调制以及动态电荷条带的出现。我们认为它们的表现既有非磁性参考化合物$ $ _ {12} $的特性，又在$ r \ mathrm {b} _ {12} $ antiferRomagnets的相图中，这些抗FiferRomagnets在马尔赛语中表现出多个具有各向异性磁场相图的磁性相。我们还讨论了Ybb $ _ {12} $和基于YB的十二烷的金属 - 绝缘体过渡，从Yb 4 $ f $ -f $ -electron构型的不稳定性方面，除了硼笼的Jahn-Teller稳定性外，还出现了，提供了一种电荷和旋转的一种机制，并提供了一种机制。实验结果挑战了在YBB $ _ {12} $中已建立的Kondo-runsulator场景，提供了有利于出现YB-YB振动耦合对的参数，该对应被视为负责负荷和自旋差异的主要因素。
The physical properties of rare-earth (RE) dodecaborides, characterized by a cage-glass crystal structure with loosely bound RE ions, are reviewed. These compounds are strongly correlated electron systems with simultaneously active charge, spin, orbital, and lattice degrees of freedom, which explains the complexity of all $R\mathrm{B}_{12}$ compounds including antiferromagnetic (TbB$_{12}$-TmB$_{12}$) and nonmagnetic (LuB$_{12}$) metals, on one side, and the so-called Kondo insulator compound YbB$_{12}$ and Yb-based Yb$_{x}R_{1-x}$B$_{12}$ solid solutions, on the other. The development of the cooperative dynamic Jahn-Teller instability of the covalent boron network produces trigonal and tetragonal distortions of the rigid cage and results in the symmetry lowering of the fcc lattice in the dodecaborides. The ferrodistortive dynamics in the boron sub-lattice generates both the collective modes and quasilocal vibrations (rattling modes) of the heavy RE ions, causing a modulation in the charge-carrier density and the emergence of dynamic charge stripes. We consider their manifestations both in the properties of the nonmagnetic reference compound LuB$_{12}$ and in the phase diagrams of the $R\mathrm{B}_{12}$ antiferromagnets that exhibit multiple magnetic phases with anisotropic field-angular phase diagrams in the form of the Maltese cross. We also discuss the metal-insulator transitions in YbB$_{12}$ and Yb-based dodecaborides in terms of the instability of the Yb 4$f$-electron configuration, which appears in addition to the Jahn-Teller instability of the boron cage, providing one more mechanism of the charge and spin fluctuations. The experimental results challenge the established Kondo-insulator scenario in YbB$_{12}$, providing arguments in favor of the appearance of Yb-Yb vibrationally coupled pairs which should be considered as the main factor responsible for the charge- and spin-gap formation.
