中性-离子跃迁系统中的相位竞争、孤子和畴壁
Phase Competition, Solitons, and Domain Walls in Neutral-Ionic Transition Systems
摘要：
从理论上全面研究了一维中性-离子跃迁系统中的相竞争和激发。从玻色化哈密顿量的半经典处理出发，我们研究了中性态（N）、铁电离子态（I $_\mathrm{ferro}$）和顺电离子态（I $_\mathrm{para}$）之间的竞争。当考虑涨落引起的高阶可公度性势时，它们之间的相变可以成为一阶相变。特别地，N和I $_\mathrm{ferro}$之间的一阶相边界的描述使我们能够分析N-I $_\mathrm{ferro}$畴壁。明确地描述了在这三个阶段中的孤子激发和它们的形成能的评估跨越相边界。根据拓扑荷和自旋对孤子和畴壁激发的性质进行了分类。在分子中性离子过渡系统的实验观察的相关性进行了讨论。我们将四硫富瓦烯- $p$ -四氯苯醌（TTF-CA）在高温区的压力诱导跃迁归因于从N到I $_\mathrm{para}$态的跃迁，并讨论了其结果。
英文摘要：
Phase competition and excitations in the one-dimensional neutral-ionic transition systems are theoretically studied comprehensively. From the semiclassical treatment of the bosonized Hamiltonian, we examine the competition among the neutral (N), ferroelectric-ionic (I$_\mathrm{ferro}$) and paraelectric-ionic (I$_\mathrm{para}$) states. The phase transitions between them can become first-order when the fluctuation-induced higher-order commensurability potential is considered. In particular, the description of the first-order phase boundary between N and I$_\mathrm{ferro}$ enables us to analyze N-I$_\mathrm{ferro}$ domain walls. Soliton excitations in the three phases are described explicitly and their formation energies are evaluated across the phase boundaries. The characters of the soliton and domain-wall excitations are classified in terms of the topological charge and spin. The relevance to the experimental observations in the molecular neutral-ionic transition systems is discussed. We ascribe the pressure-induced crossover in tetrathiafulvalene-$p$-chloranil (TTF-CA) at a high-temperature region to that from the N to the I$_\mathrm{para}$ state, and discuss its consequence.
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