Polarization Switching of Layer‐Degenerate Valley Trions in Even‐Layered MoSe 2

The valley‐coupled tightly bound electrons and holes in two‐dimensional transition metal dichalcogenides (TMDs) lead to a rich spectrum of valley many‐body complexes with intricate fine structures. Introducing layer degrees of freedom in multilayer systems offers additional control over valley polarization and coherence of excitonic complexes via layer‐valley coupling. In this study, we investigate the layer degenerate states in even‐layer MoSe 2 , in contrast to odd‐layer with non‐degeneracy. Through photoluminescence (PL) and transient absorption (TA) spectroscopy, we reveal that even‐layer MoSe 2 predominantly forms robust trions at room temperature, unlike the excitons in odd‐layer. We identify a novel interlayer trion in even‐layer: the layer degenerate valley trion, characterized by a larger binding energy than intralayer trions in odd‐layer. Our dynamical analysis uncovers a direct formation process with faster time for these trions, driven by strong interlayer coupling within a layer degenerate valley. Additionally, we demonstrate switching between layer‐degenerate and non‐degenerate trions with valley polarization ranging from 0% to 25%, enabled by electrically tunable layer degeneracy and Berry curvature. These findings provide insights into the role of layer degeneracy in many‐body complex formation and open new avenues for quantum information modulation.