超越能带拓扑的量子涡旋激子
Quantum-vortex excitons beyond band topology
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中文总结 AI 辅助
本文研究平坦陈带中激子的拓扑性质，发现库仑相位匹配可稳定量子涡旋激子，并通过自旋轨道耦合调控其与零环绕态的转变，建立了激子拓扑与光学响应的微观联系。
中文摘要 AI 辅助
光学激发典型的低维半导体，其最低能量的束缚态通常是无节点的s型激子。在此，我们解释了库仑相位匹配如何在平坦陈带中稳定量子涡旋激子作为最低束缚态。利用典型的阴阳kagome晶格，我们证明增加自旋-轨道耦合会驱动最低激子从量子涡旋态转变为零环绕态，同时保持能带陈数不变。我们将这种行为归因于激子相位差和Bloch重叠相位的规范不变组合，该组合可以降低库仑能。通过比较具有相同波函数振幅的状态，我们分离出这一相位贡献，并表明它足以驱动激子排序的反转。我们通过动量空间波函数相对于导带-价带陈数差的环绕来对激子拓扑进行分类，将竞争态与圆偏振选择规则联系起来。然后我们展示，由此产生的重排可以直接在光学吸收光谱中追踪，通过从暗涡旋激子到亮零环绕激子的转变。这些发现建立了激子拓扑、库仑束缚和光学响应之间的微观联系，这种联系超越了底层电子能带陈数所包含的信息。
英文摘要
Optically exciting a typical low-dimensional semiconductor produces a nodeless \(s\)-type exciton as its lowest-energy bound state. Here, we explain how Coulomb phase matching stabilises a quantum-vortex exciton as the lowest bound state in flat Chern bands. Using a prototypical Yin--Yang kagome lattice, we demonstrate that increasing the spin--orbit coupling drives a transition of the lowest exciton from a quantum-vortex state to a zero-winding state, while leaving the band Chern numbers unchanged. We trace this behaviour to a gauge-invariant combination of exciton phase differences and Bloch-overlap phases that can reduce the Coulomb energy. By comparing states with identical wavefunction amplitudes, we isolate this phase contribution and show that it is sufficient to drive the reversal in exciton ordering. We classify exciton topology by the momentum-space wavefunction winding relative to the conduction--valence Chern-number difference,connecting the competing states to circular-polarisation selection rules. We then show that the resulting reordering can be tracked directly in the optical absorption spectrum, through the transition from a dark vortex exciton to a bright zero-winding exciton. These findings establish a microscopic link between exciton topology, Coulomb binding, and optical response that extends beyond the information contained in the underlying electronic band Chern numbers.
发表机构
- Hanyang University（汉阳大学）
- Ajou University（亚洲大学）
- Asia Pacific Center for Theoretical Physics（亚太理论物理中心）
- University of Cambridge（剑桥大学）
机构由 AI 辅助整理，请以论文原文为准。
