Anomalously robust valley polarization and valley coherence in bilayer WS ₂

Significance Coherence of electronic states is crucial for quantum manipulation through light–matter interactions. To achieve coherence in conventional solid-state systems, extreme conditions such as cryogenic temperatures are required, which is a long-term challenge for practical applications. The emerging atomically thin transition metal dichalcogenides provide an unprecedented platform to explore the interplay of quantum states of spin and valley. In this paper, we demonstrate room-temperature valley coherence and valley polarization in bilayer WS 2 with polarization-resolved photoluminescence measurements. The robustness of the valley coherence and valley polarization is understood as the consequence of the coupling of spin, layer, and valley degrees of freedom in bilayer WS 2 . It inspires new perspectives on quantum manipulations in 2D solid-state systems.