论文标题
（nbse $ _4 $）的带结构$ _ 3 $ i和（tase $ _4 $）$ _ 3 $ i：调和运输，光学和ARPES
Band structures of (NbSe$_4$)$_3$I and (TaSe$_4$)$_3$I: Reconciling transport, optics and ARPES
论文作者
论文摘要
在准一维过渡金属四核化合物（MSE $ _4 $）中，$ _ n $ i（m = nb，ta），$ n = 3 $化合物是唯一未显示电荷密度波的$ n = 3 $化合物。相反，它们显示出令人困惑的运输行为的结构过渡。它们是最低温度下的半导体，但它们的传输差异明显小于ARPES和光学电导率的传输差异。最近，与先前的报道相比，已经发现了（tase $ _4 $）$ _ 3 $ i的金属多型在低温下并存。在这项工作中，我们介绍了不同的（MSE $ _4 $）$ _ n $我报告的结构的详细的Ab-Initio和紧密的绑定带结构计算。我们与观察到的传输缝隙获得了良好的一致性，并解释了ARPES和光学实验如何由于近似翻译对称性而有效地探测不同频段之间的间隙，从而解决了争议。最后，我们展示了小的外部孔掺杂如何通过（tase $ _4 $）$ _ 3 $ i中的van霍夫奇异性调整费米水平，并讨论对磁性和超导性的影响。
Among the quasi one-dimensional transition metal tetrachalcogenides (MSe$_4$)$_n$I (M=Nb,Ta), the $n=3$ compounds are the only ones not displaying charge density waves. Instead, they show structural transitions with puzzling transport behavior. They are semiconductors at the lowest temperatures, but their transport gaps are significantly smaller than those inferred from ARPES and optical conductivity. Recently, a metallic polytype of (TaSe$_4$)$_3$I has been found with ferromagnetism and superconductivity coexisting at low temperature, in contrast to previous reports. In this work we present detailed ab-initio and tight binding band structure calculations for the different (MSe$_4$)$_n$I reported structures. We obtain good agreement with the observed transport gaps, and explain how ARPES and optics experiments effectively probe a gap between different bands due to an approximate translation symmetry, solving the controversy. Finally, we show how small extrinsic hole doping can tune the Fermi level through a Van Hove singularity in (TaSe$_4$)$_3$I and discuss the implications for magnetism and superconductivity.
