发表机构
Institute for Materials Research, Tohoku University（东北大学物质材料研究所学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出电荷-赝自旋模型，揭示电荷有序系统中携带±2e电荷的集体玻色子激发（双荷子），并证明其可产生Seebeck效应及交流驱动的直流电流，扩展了磁振子范式至电荷领域。
AI 中文摘要
电荷序通常以电子密度的静态调制为特征，而其集体激发在准粒子视角下的发展程度不如自旋有序系统中的集体激发。在此，我们在一个有效的电荷-赝自旋模型中阐述了电荷序的集体激发，其中电荷有序基态由交错的赝自旋序表示。通过Holstein-Primakoff变换对该有序态周围的涨落进行量子化，我们揭示了两个玻色子准粒子分支，它们具有简并的、有能隙的色散，并携带相反的量子化电荷±2e。因此，我们将这些电荷-2e玻色子称为“双荷子”（bichargons），这与双分次反铁磁体的两个携带相反自旋角动量的磁振子分支密切相关。我们表明，温度梯度驱动热激发双荷子的扩散，当通过将化学势调离电荷中性点来解除相反电荷分支之间的简并时，会产生电荷Seebeck响应。相反，尽管携带有限电荷，热双荷子气体在静态电场下仍保持电绝缘，因为双荷子准粒子数不守恒。然而，交流电场可以参数化地产生成对的相反电荷双荷子，这些双荷子在偏置电场存在下支持有限的直流漂移电流，提供了半导体中由光激发电子-空穴对介导的光电导性的玻色子类比。我们的结果确立了双荷子作为电荷有序系统中新一类集体玻色子电荷载流子，并将自旋有序系统中磁振子的准粒子范式扩展到电荷领域，以电荷取代自旋角动量作为输运量。
英文摘要
Charge order is conventionally characterized by a static modulation of the electronic density, while its collective excitations remain less developed from a quasiparticle perspective than those of spin-ordered systems. Here, we formulate the collective excititations of charge order within an effective charge-pseudospin model, in which the charge-ordered ground state is represented by staggered pseudospin order. Quantizing fluctuations around this ordered state via a Holstein--Primakoff transformation, we reveal two branches of bosonic quasiparticles with degenerate, gapped dispersions that carry opposite quantized electric charges $\pm 2e$. We therefore term these charge-$2e$ bosons ``\textit{bichargons},'' closely paralleling the two magnon branches of a bipartite antiferromagnet that carry opposite spin angular momenta. We show that a temperature gradient drives the diffusion of thermally excited bichargons, generating a charge Seebeck response when the degeneracy between the oppositely charged branches is lifted by tuning the chemical potential away from the charge-neutrality point. In contrast, despite carrying finite electric charges, a thermal bichargon gas remains electrically insulating under a static electric field because bichargon quasiparticle number is not conserved. An ac electric field, however, can parametrically generate coherent pairs of oppositely charged bichargons that support a finite dc drift current in the presence of a bias electric field, offering a bosonic analogue of photoconductivity mediated by photoexcited electron--hole pairs in semiconductors. Our results establish bichargons as a new class of collective bosonic charge carriers in charge-ordered systems and extend the quasiparticle paradigm of magnons in spin-ordered systems to the charge sector, with electric charge replacing spin angular momentum as the transported quantity.
