Thouless’ quantization of adiabatic particle transport permits one 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 nontrivial 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 nonstoichiometric 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 nontrivial transport regime such that most of the total charge current results to be uncorrelated from the ionic ones.

中文翻译：

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非化学计量电解质中的氧化态，Thouless泵和非平凡离子传输。

绝热粒子传输的无量量化使人们可以将整数拓扑电荷与电子缺口材料的每个原子相关联。如果这些电荷是可加和独立于原子位置的，则它们提供了原子氧化态的严格定义，并且原子可以被识别为离子导体中的整数电荷载体。只要满足这些条件，电荷传输就必然是对流的。也就是说，没有大量的离子流就不可能发生这种离子流，这是我们认为微不足道的一种传输方式。我们表明，允许打破这些条件的拓扑要求与如果系统受适当定义的时间周期哈密顿量决定的Thouless泵机制相同。这些要求的出现决定了非平凡的传输方式，即使在电子绝缘体中，电荷也可以在没有任何离子对流的情况下流动。首先用几个简单的分子模型证明了这些结果，这些模型在引入原子位置沿构型空间中的闭环的虚拟时间依赖性时显示了量子泵机制。最后，我们检查了我们的发现对非化学计量的碱金属卤化物熔体传输性质的影响，在相同的拓扑条件下，沿着配置空间中的某些闭环会引起量子泵机制的情况，也决定了非平凡的传输方式，因此大多数总充电电流与离子电荷无关。