False metals, real insulators, and degenerate gapped metals
False metals, real insulators, and degenerate gapped metals
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DOI：
10.1063/5.0015322
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发表时间：
2020-08
期刊：
影响因子：
--
通讯作者：
O. Malyi;A. Zunger
中科院分区：
文献类型：
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作者：
O. Malyi;A. Zunger
随着导体科学和技术从研究简单的元素金属如Al或Cu过渡到研究化合物导体如二元或三元氧化物和磷属元素化物，一类特殊的简并但带隙的金属已经被注意到。它们假定的电子组态显示费米能级在导带或价带内，但在主带边之间存在“内部带隙”。这种电子结构的重要性在于，当内部带隙内状态的形成所消耗的能量小于通过将载流子从导带转移到这些较低能量的受体状态而获得的能量时，它可能对内部带隙内状态的形成不稳定，从而将原始（假）金属改变为绝缘体。类似的过程也存在于费米能在价带内的简并但带隙的金属中，其中能量增益由电子从施主能级转移到价带的未占据部分来定义。我们在这里关注的事实是，许多电子结构方法忽略了一些可以稳定绝缘替代物的物理因素，而是预测了实际上不存在的假金属（注意，这通常不是物理相变，而是对先前理论错误的纠正，导致了对金属的错误预测）。
As science and technology of conductors have transitioned from studying simple elemental metals such as Al or Cu to compound conductors such as binary or ternary oxides and pnictides, a special class of degenerate but gapped metals has been noticed. Their presumed electronic configurations show the Fermi level inside the conduction band or valence band, yet there is an "internal band gap" between the principal band edges. The significance of this electronic configuration is that it might be unstable towards the formation of states inside the internal band gap when the formation of such states costs less energy than the energy gained by transferring carriers from the conduction band to these lower energy acceptor states, changing the original (false) metal to an insulator. The analogous process also exists for degenerate but gapped metals with Fermi energy inside the valence band, where the energy gain is defined by transfer of electrons from the donor level to the unoccupied part of the valence band. We focus here on the fact that numerous electronic structure methodologies have overlooked some physical factors that could stabilize the insulating alternative, predicting instead false metals that do not really exist (note, this is in general not a physical phase transition but a correction of a previous error in theory that led to a false prediction of a metal).