Spin-triplet topological excitonic insulators in two-dimensional materials

作者：Huaiyuan Yang, Jia-Xi Zeng, Yu-Chuan Shao, Yuanfeng Xu, X. Dai, Xin-Zheng Li · 发表于：Physical review B · 年份：2023 · DOI：10.1103/physrevb.109.075167 · 被引用次数：10 · 研究领域：Physics

Quantum spin-hall insulator (QSHI) processes nontrivial topology. We notice that the electronic structures of some particular QSHIs are favorable for realization of excitonic insulators (EIs). Using first-principles many-body perturbation theory ($GW$+BSE) and $k \cdot p$ model, we show that high-temperature ($T$) topological EIs with unlike spin can exist in such QSHIs with non-vanishing band gaps, e.g. 2D AsO and $\text{Mo}_2\text{Ti}\text{C}_2\text{O}_2$. Spin-triplet type EI phase induced by strong electron-hole interaction preserves time-reversal symmetry and the topological characteristics. A novel optical selection rule exists, upon going through the phase transition from the normal QSHIs to the topological EIs, absorption spectroscopy shows pronounced $T$-dependent changes, providing guidance for future experimental detections. The demonstrated coupling between EIs and topology also means that rich physics exists in such materials which retain such interdisciplinary features.