Temperature-driven narrowing of the insulating gap as a precursor of the insulator-to-metal transition: Implications for the electronic structure of solids.
Temperature-driven narrowing of the insulating gap as a precursor of the insulator-to-metal transition: Implications for the electronic structure of solids.
复制标题
温度驱动的绝缘间隙变窄是绝缘体到金属转变的前兆：对固体电子结构的影响。
DOI：
--
复制
发表时间：
2018
影响因子：
4.4
通讯作者：
A. Kurnosov
中科院分区：
文献类型：
--
作者：
V. Lubchenko;A. Kurnosov
我们提出了一个微观图片，合理地解释了在绝缘体、晶体或其他材料中，带隙随温度的惊人急剧下降。这种间隙的缩小主要是由于长波光学声子的波动——当后者存在时，或者如果材料是无定形的，它们的无序类似物。我们详细阐述了这一概念，以表明除了由闭壳电子构型构成的弱束缚固体外，周期性固体中存在绝缘隙或赝隙意味着光学声子也必须存在。这意味着在绝缘固体中，原始细胞必须至少有两个原子和/或电荷密度波存在，可能的例外是弱键固体，如稀有气体或铁磁维格纳晶体。作为一个推论，通过非闭合壳层相互作用结合在一起的（周期性）元素固体，其基本单元只包含一个原子，通常是金属，与观察一致。讨论了当前图像对维格纳固体的影响。建立了金属-绝缘子跃迁的简单场论，将金属-绝缘子跃迁的长波光振动与序参量的波动直接联系起来。order参数显示至少有两个分量，但没有Goldstone模态出现作为转换的结果。
We present a microscopic picture rationalizing the surprisingly steep decrease in the bandgap with temperature in insulators, crystalline or otherwise. The gap narrowing largely results from fluctuations of long-wavelength optical phonons-when the latter are present-or their disordered analogs if the material is amorphous. We elaborate on this notion to show that possibly with the exception of weakly bound solids made of closed-shell electronic configurations, the existence of an insulating gap or pseudogap in a periodic solid implies that optical phonons must be present, too. This means that in an insulating solid, the primitive cell must have at least two atoms and/or that a charge density wave is present, with the possible exception of weakly bonded solids such as rare-gas or ferromagnetic Wigner crystals. As a corollary, a (periodic) elemental solid held together by nonclosed shell interactions and whose primitive unit contains only one atom will ordinarily be a metal, consistent with observation. Consequences of the present picture for Wigner solids are discussed. A simple field theory of the metal-insulator transition is constructed that directly ties long-wavelength optical vibrations with fluctuations of an order parameter for the metal-insulator transition. The order parameter is shown to have at least two components, yet no Goldstone mode arises as a result of the transition.