Gate-tunable chiral spin mode in WSe(2)/WS(2) moiré superlattices.

A gate-tunable chiral spin mode with giant Raman efficiency was observed in near-0° twisted WSe2/WS2 bilayers, transitioning from a chiral spin exciton to an excitonic polaron.

• Why it matters: Understanding collective spin excitations in solids is crucial for advancing spintronics and quantum information technologies, yet such phenomena remain largely unexplored in transition metal dichalcogenide moiré superlattices.
• What they did: Researchers used Raman spectroscopy to identify a sharp resonance linked to the chiral spin mode, varying the filling to observe its transition and confirming its spin-flip nature via the Zeeman effect, in a system with charge-transfer insulator characteristics at unity filling.
• The result: The findings suggest that transition metal-dichalcogenide moiré superlattices are a promising platform for studying exotic low-lying collective excitations, opening avenues for future spin-based device applications.