Han, BoBoHanFitzgerald, Jamie M.Jamie M.FitzgeraldLackner, LukasLukasLacknerRosati, RobertoRobertoRosatiEsmann, MartinMartinEsmannEilenberger, FalkFalkEilenbergerTaniguchi, TakashiTakashiTaniguchiWatanabe, KenjiKenjiWatanabeSyperek, MarcinMarcinSyperekMalić, ErminErminMalićSchneider, ChristianChristianSchneider2025-04-042025-04-042025https://publica.fraunhofer.de/handle/publica/48616210.1103/PhysRevLett.134.0769022-s2.0-85218959288MoTe2 monolayers and bilayers are unique within the family of van der Waals materials since they pave the way toward atomically thin infrared light-matter quantum interfaces, potentially reaching the important telecommunication windows. Here, we report emergent exciton polaritons based on MoTe2 monolayers and bilayers in a low-temperature open microcavity in a joint experiment-theory study. Our experiments clearly evidence both the enhanced oscillator strength and enhanced luminescence of MoTe2 bilayers, signified by a 38% increase of the Rabi splitting and a strongly enhanced relaxation of polaritons to low-energy states. The latter is distinct from polaritons in MoTe2 monolayers, which feature a bottlenecklike relaxation inhibition. Both the polaritonic spin valley locking in monolayers and the spin-layer locking in bilayers are revealed via the Zeeman effect, which we map and control via the light-matter composition of our polaritonic resonances.entruejournal article