发表机构
Stanford University; Aarhus University; Università degli Studi di Trieste; Elettra - Sincrotrone Trieste S.C.p.A.; Tohoku University; Technical University of Denmark（斯坦福大学; 奥胡斯大学; 的里雅斯特大学; Elettra-的里雅斯特同步辐射中心; 东北大学; 丹麦技术大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过时间分辨光电子能谱在磁性拓扑绝缘体MnBi$_2$Te$_4$中观察到微秒级寿命的激子凝聚态光谱特征，表明该材料是研究光致多体态与拓扑磁性相互作用的理想平台。
AI 中文摘要
激子凝聚是由束缚电子-空穴对的宏观相干性产生的长期寻求的关联量子态。尽管在多种材料平台中已报道了平衡态和瞬态激子态，但作为体态量子材料的内在属性，光诱导激子凝聚态的直接证据一直难以获得。在此，我们利用时间分辨和角分辨光电子能谱研究了本征磁性拓扑绝缘体MnBi$_2$Te$_4$中长寿命的光激发载流子，并通过Sb替代将化学势调谐至拓扑表面态。在光学激发后，我们观察到瞬态态的延迟出现，其形成与体导带的耗尽同时发生，且其寿命延伸至微秒时间尺度。准粒子色散表现出明显的平坦化，并形成墨西哥帽状轮廓。这些光谱特征与亚稳激子凝聚态的形成一致。我们的结果确立了磁性拓扑绝缘体作为研究长寿命光致多体态及其与拓扑和磁性相互作用的 promising 平台。
英文摘要
Exciton condensates are long-sought correlated quantum states arising from macroscopic coherence of bound electron-hole pairs. Although equilibrium and transient excitonic states have been reported in several material platforms, direct evidence for a light-induced exciton condensate state has been challenging to achieve as an intrinsic property of a bulk quantum material. Here, we use time- and angle-resolved photoemission spectroscopy to investigate long-lived photoexcited carriers in the intrinsic magnetic topological insulator MnBi$_2$Te$_4$ with the chemical potential tuned to the topological surface state by Sb substitution. Following optical excitation, we observe the delayed emergence of a transient state whose formation coincides with depopulation of the bulk conduction band and whose lifetime extends to the microsecond timescale. The quasiparticle dispersion exhibits a pronounced flattening and develops a Mexican-hat-like profile. These spectral signatures are consistent with the formation of a metastable excitonic condensate state. Our results establish magnetic topological insulators as a promising platform for investigating long-lived photoinduced many-body states and their interplay with topology and magnetism.
Comments21 pages, 8 figures
