氧化态、Thouless泵与非化学计量电解质中的非平凡离子输运
Oxidation states, Thouless' pumps, and non-trivial ionic transport in non-stoichiometric electrolytes
AI总结：
本文基于Thouless量子化探讨电子带隙材料的氧化态与离子输运，提出打破拓扑条件可实现无离子对流的非平凡电荷输运，并在分子模型与非化学计量碱卤化物熔体中验证了该机制。
摘要：
Thouless的绝热粒子输运量子化允许为电子带隙材料中的每个原子关联一个整数拓扑荷。如果这些电荷是可加的且与原子位置无关，它们就提供了原子氧化态的严格定义，原子可被识别为离子导体中的整数电荷载流子。每当满足这些条件时，电荷输运必然是对流性的，即没有大量离子流就不会发生，我们将这种输运机制称为平凡机制。我们表明，允许打破这些条件的拓扑要求，与系统在受适当定义的时间周期性Hamiltonian作用时决定Thouless泵机制的拓扑要求相同。这些要求的出现决定了一种非平凡输运机制，即无需任何离子对流电荷即可流动，甚至在电子绝缘体中也是如此。这些结果首先通过几个简单分子模型得到证明，这些模型在引入沿位形空间中闭合回路的原子位置虚构时间依赖性后，展现出量子泵机制。最后，我们考察了这些发现对非化学计量碱卤化物熔体输运性质的影响，其中沿位形空间中某些闭合回路会诱导量子泵机制的相同拓扑条件，也决定了一种非平凡输运机制，使得大部分总电流与离子电流不相关。
英文摘要：
Thouless' quantization of adiabatic particle transport permits to associate an integer topological charge with each atom of an electronically gapped material. If these charges are additive and independent of atomic positions, they provide a rigorous definition of atomic oxidation states and atoms can be identified as integer-charge carriers in ionic conductors. Whenever these conditions are met, charge transport is necessarily convective, i.e. it cannot occur without substantial ionic flow, a transport regime that we dub trivial. We show that the topological requirements that allow these conditions to be broken are the same that would determine a Thouless' pump mechanism if the system were subject to a suitably defined time-periodic Hamiltonian. The occurrence of these requirements determines a non-trivial transport regime whereby charge can flow without any ionic convection, even in electronic insulators. These results are first demonstrated with a couple of simple molecular models that display a quantum pump mechanism upon introduction of a fictitious time dependence of the atomic positions along a closed loop in configuration space. We finally examine the impact of our findings on the transport properties of non-stoichiometric alkali-halide melts, where the same topological conditions that would induce a quantum pump mechanism along certain closed loops in configuration space also determine a non-trivial transport regime such that most of the total charge current results to be uncorrelated from the ionic ones.
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