阻挫三角晶格团簇磁体LiZn $_{2-x}$ Mo $_3$ O $_8$的电子调谐性
Electronic tunability of the frustrated triangular-lattice cluster magnet LiZn$_{2-x}$Mo$_3$O$_8$
摘要：
LiZn $_2$ Mo $_3$ O $_8$是一种电绝缘的几何阻挫反铁磁体，其中无机Mo $_3$ O $_{13}$团簇每个都表现为单个$S = 1/2$单元，团簇排列在二维三角形晶格上。先前的结果已经表明，LiZn $_2$ Mo $_3$ O $_8$在低至至少$T = 0.05\,K$时不表现出静态磁序，而是具有价键基态。在这里，我们表明，锂锌$_2$钼$_3$ O $_8$可以通过氧化与$\mathrm{I}_2$和随后的去除$\mathrm{Zn}^{2+}$阳离子，以访问整个范围内的电子计数，从一个到零的未成对电子的三角形晶格上的每个站点进行空穴掺杂。与预期相反，没有金属状态诱导，相反，主要的效果是抑制的网站有助于凝聚价键状态的数量。此外，衍射和对分布函数分析显示，没有证据表明局部Jahn-Teller扭曲或其他偏离母三角对称作为掺杂或温度的函数。两者合计，数据和密度泛函理论计算表明，从磁性层中去除电子有利于安德森本地化所产生的空穴和增加的电气带隙形成的金属和超导状态。这些结果对从母体绝缘几何阻挫反铁磁体实现金属态所需的化学条件提出了严格的限制。
英文摘要：
LiZn$_2$Mo$_3$O$_8$ is an electrically insulating geometrically frustrated antiferromagnet in which inorganic Mo$_3$O$_{13}$ clusters each behaves as a single $S = 1/2$ unit, with the clusters arranged on a two-dimensional triangular lattice. Prior results have shown that LiZn$_2$Mo$_3$O$_8$ does not exhibit static magnetic order down to at least $T = 0.05\,K$, and instead possesses a valence bond ground state. Here, we show that LiZn$_2$Mo$_3$O$_8$ can be hole doped by oxidation with $\mathrm{I}_2$ and subsequent removal of $\mathrm{Zn}^{2+}$ cations to access the entire range of electron count, from one to zero unpaired electrons per site on the triangular lattice. Contrary to expectations, no metallic state is induced; instead, the primary effect is to suppress the number of sites contributing to the condensed valence-bond state. Further, diffraction and pair-distribution function analysis show no evidence for local Jahn-Teller distortions or other deviations from the parent trigonal symmetry as a function of doping or temperature. Taken together, the data and density functional theory calculations indicate that removal of electrons from the magnetic layers favors Anderson localization of the resulting hole and an increase in the electrical band-gap over the formation of a metallic and superconducting state. These results put strong constraints on the chemical conditions necessary to realize metallic states from parent insulating geometrically frustrated antiferromagnets.
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