Trion sensing of a zero-field composite Fermi liquid

• 成果类型: Article
• 署名作者: Anderson, Eric; Cai, Jiaqi; Reddy, Aidan P.; Park, Heonjoon; Holtzmann, William; Davis, Kai; Taniguchi, Takashi; Watanabe, Kenji; Smolenski, Tomasz; Imamoglu, Atac; Cao, Ting; Xiao, Di; Fu, Liang; Yao, Wang; Xu, Xiaodong
• 署名单位: University of Washington; University of Washington Seattle; Massachusetts Institute of Technology (MIT); University of Washington; University of Washington Seattle; National Institute for Materials Science; National Institute for Materials Science; Swiss Federal Institutes of Technology Domain; ETH Zurich; University of Hong Kong
• 刊物名称: Nature
• ISSN/ISSBN: 0028-4554
• DOI: 10.1038/s41586-024-08134-0
• 发表日期: 2024-11-21
• 关键词: quantum; real

摘要

The half-filled lowest Landau level is a fascinating platform for researching interacting topological phases. A celebrated example is the composite Fermi liquid, a non-Fermi liquid formed by composite fermions in strong magnetic fields1-10. Its zero-field counterpart is predicted in a twisted MoTe2 bilayer (tMoTe2)11,12-a recently discovered fractional Chern insulator exhibiting the fractional quantum anomalous Hall effect13-16. Although transport measurements at nu = -1/2 show signatures consistent with a zero-field composite Fermi liquid14, new probes are crucial to investigate the state and its elementary excitations. Here, by using the unique valley properties of tMoTe2, we report optical signatures of a zero-field composite Fermi liquid. We measured the degree of circular polarization (rho) of trion photoluminescence versus hole doping and electric field. We found that, within the phase space showing robust ferromagnetism, rho is near unity for Fermi liquid states. However, rho is quenched at both integer and fractional Chern insulators, and in a hole doping range near nu = -1/2. Temperature, optical excitation power and electric-field-dependence measurements demonstrate that the quenching of rho is a direct consequence of an energy gap (pseudogap) for electronic excitations of the Chern insulators (composite Fermi liquid): because the local spin-polarized excitations necessary to form trions are strongly suppressed, trion formation at the corresponding filling factors relies on optically generated unpolarized itinerant holes. Our work highlights a new excitonic probe of zero-field fractional Chern insulator physics, unique to tMoTe2. Using the unique valley properties of a twisted MoTe2 bilayer, measurements of the degree of circular polarization of trion photoluminescence reveal optical signatures of a zero-field composite Fermi liquid.