近日，美国华盛顿大学的许晓栋教授及其研究团队取得一项新进展。经过不懈努力，他们实现零场复合费米液体的三重子传感。相关研究成果已于2024年11月20日在国际权威学术期刊《自然》上发表。

本研究利用扭曲二碲化钼（tMoTe₂）独特的谷特性，报道了零磁场复合费米液体的光学特征。研究人员测量了三重子光致发光的圆偏振度（ρ）随空穴掺杂和电场的变化。研究发现，在表现出强铁磁性的相空间内，费米液体状态的ρ接近1。

然而，在整数和分数量子陈绝缘体以及空穴掺杂量接近ν=-1/2的范围内，ρ被抑制。通过温度、光激发功率和电场依赖性的测量，研究人员证明ρ的抑制是陈绝缘体（复合费米液体）电子激发能隙（伪能隙）的直接结果——由于形成三重子所需的局部自旋极化激发被强烈抑制，因此在相应的填充因子下，三重子的形成依赖于光学产生的非极化流动空穴。这项研究工作突出了一种独特的三重子探针，用于探索tMoTe?中独有的零磁场分数量子陈绝缘体物理。

据悉，半填充的最低朗道能级是研究相互作用拓扑相的一个迷人平台。一个著名的例子是复合费米液体，它是由强磁场中的复合费米子形成的非费米液体。其零磁场对应物被预测存在于扭曲的二碲化钼双层（tMoTe₂）中——这是一种最近发现的分数量子陈绝缘体，表现出分数量子反常霍尔效应。尽管在ν=-1/2时的输运测量结果显示出与零磁场复合费米液体一致的特征，但要深入研究该状态及其基本激发，新的探测手段至关重要。

附：英文原文

Title: Trion sensing of a zero-field composite Fermi liquid

Author: Anderson, Eric, Cai, Jiaqi, Reddy, Aidan P., Park, Heonjoon, Holtzmann, William, Davis, Kai, Taniguchi, Takashi, Watanabe, Kenji, Smolenski, Tomasz, Imamolu, Ata, Cao, Ting, Xiao, Di, Fu, Liang, Yao, Wang, Xu, Xiaodong

Issue&Volume: 2024-11-20

Abstract: 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 fields. Its zero-field counterpart is predicted in a twisted MoTe₂ bilayer (tMoTe₂)—a recently discovered fractional Chern insulator exhibiting the fractional quantum anomalous Hall effect. Although transport measurements at ν=-1/2 show signatures consistent with a zero-field composite Fermi liquid, 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 (ρ) of trion photoluminescence versus hole doping and electric field. We found that, within the phase space showing robust ferromagnetism, ρ is near unity for Fermi liquid states. However, ρ is quenched at both integer and fractional Chern insulators, and in a hole doping range near ν=-1/2. Temperature, optical excitation power and electric-field-dependence measurements demonstrate that the quenching of ρ 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.

DOI: 10.1038/s41586-024-08134-0

Source: https://www.nature.com/articles/s41586-024-08134-0