论文标题
kagome金属中的双范·霍夫（Van Hove）奇异性的手性激发秩序
Chiral excitonic order from twofold van Hove singularities in kagome metals
论文作者
论文摘要
Kagome Metals AV $ _3 $ SB $ _5 $（A = K，RB，CS）的最新实验[M. Kang等人，Nat。物理。 18, 301-308 (2022)] identify twofold van Hove singularities (TvHS) with opposite concavity near the Fermi energy, generating two approximately hexagonal Fermi surfaces -- one electron-like and the other hole-like. Here we propose that a TvHS generates a novel time-reversal symmetry breaking excitonic order -- arising due to bound pairs of electrons and holes located at opposite concavity van Hove singularities. We introduce a minimal model for the TvHS and investigate interaction induced many-body instabilities via the perturbative renormalisation group technique and a free energy analysis. Specialising to parameters appropriate for the kagome metals AV$_3$Sb$_5$, we construct a phase diagram comprising chiral excitons, charge density wave and a region of coexistence.我们建议这是对AV $ _3 $ sb $ _5 $的各种实验观测的解释。 Notably, the chiral excitonic state gives rise to a quantum anomalous Hall conductance, providing an appealing interpretation of the observed anomalous Hall effect in kagome metals.还讨论了双层材料中TVHS机制的可能替代实现。 We suggest that TvHS open up interesting possibilities for correlated phases, enriching the set of competing ground states to include excitonic order.
Recent experiments on kagome metals AV$_3$Sb$_5$ (A=K,Rb,Cs) [M. Kang et al., Nat. Phys. 18, 301-308 (2022)] identify twofold van Hove singularities (TvHS) with opposite concavity near the Fermi energy, generating two approximately hexagonal Fermi surfaces -- one electron-like and the other hole-like. Here we propose that a TvHS generates a novel time-reversal symmetry breaking excitonic order -- arising due to bound pairs of electrons and holes located at opposite concavity van Hove singularities. We introduce a minimal model for the TvHS and investigate interaction induced many-body instabilities via the perturbative renormalisation group technique and a free energy analysis. Specialising to parameters appropriate for the kagome metals AV$_3$Sb$_5$, we construct a phase diagram comprising chiral excitons, charge density wave and a region of coexistence. We propose this as an explanation of a diverse range of experimental observations in AV$_3$Sb$_5$. Notably, the chiral excitonic state gives rise to a quantum anomalous Hall conductance, providing an appealing interpretation of the observed anomalous Hall effect in kagome metals. Possible alternative realisations of the TvHS mechanism in bilayer materials are also discussed. We suggest that TvHS open up interesting possibilities for correlated phases, enriching the set of competing ground states to include excitonic order.
