報告摘要:

In the realm of condensed matter physics, the fractional quantum Hall effect stands as a singular experimental manifestation of topological order, characterized by the presence of anyons—quasiparticles that bear fractional charge and exhibit exchange statistics diverging from conventional fermions and bosons. This phenomenon, observed over four decades ago, was still missing the direct observation of similar topological orders arising purely from band structure—without the application of strong magnetic fields. In 2023 within the span of a few months, several pioneering experiments have illuminated this once theoretical domain. Studies on twisted homobilayer MoTe₂and pentalayer rhombohedral graphene placed on hBN have finally unveiled the existence of fractional Chern insulators (FCIs), the zero-magnetic field analog of fractional quantum Hall states.

The journey to this point, preceded by over a decade of theoretical frameworks and predictions surrounding FCIs, yet the experimental revelations have proved to be richer and more surprising than expected. In this talk, we will present how the combination of ab-initio and quantum many-body calculations can help us capture the different features observed in experiments. We will discuss the potential future for this exciting booming field, including the possible observation of fractional topological insulators, a yet-never observed topological ordered phase preserving the time reversal symmetry.

報告人簡介：

Nicolas Regnault，2001年獲XI奧賽大學/CEA-Saclay物理研究所博士學位，随後在Niall Moran從事博士後研究。先後擔任Université Paris VI助理教授及普林斯頓大學客座研究員，2023年起任巴黎高等師範學院的CNRS研究主任。曾獲得巴黎高等師範學院“Habillitation à Diriger des Recherche”和 CNRS銅牌勳章。他在博士期間進行引力可積模型的相關研究，後轉向凝聚态物理方向，是分數量子霍爾效應研究領域著名專家，尤其關注物質的拓撲相、多體量子态和非平衡量子系統中的糾纏特性等方向。發表包括Nature，Physical Review Letters等在内的論文200餘篇，累計被引11000餘次，單篇最高引用近1000次。其受邀在國際會議進行60餘次報告，曾作為合作者主辦“Moiré in Paris”等多個物理學術會議。

主要代表性成果：

[1]Kevin P. Nuckolls, Ryan L. Lee, Myungchul Oh, Dillon Wong, Tomohiro Soejima, Jung Pyo Hong, Dumitru Călugăru, Jonah Herzog-Arbeitman, B. Andrei Bernevig, Kenji Watanabe, Takashi Taniguchi, Nicolas Regnault, Michael P. Zaletel & Ali Yazdani. Quantum textures of the many-body wavefunctions in magic-angle graphene.Nature620, 525–532 (2023).

[2] B. J. Wieder, B. Bradlyn, J. Cano, Zhijun Wang, M. G. Vergniory, L. Elcoro, A. A. Soluyanov, C. Felser, T. Neupert, N. Regnault, B. A. Bernevig. Topological materials discovery from crystal symmetry.Nature Reviews Materials7, 196 (2022).

[3]S Moudgalya, S Rachel, BA Bernevig, N Regnault.Exact excited states of nonintegrable models.Physical Review B98 (23), 235155 (2018).

[4] N Regnault, BA Bernevig. Fractional Chern insulator.Physical Review X1 (2), 021014 (2011).

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