heterostructure

Monolayer transition metal dichalcogenide semiconductors (TMDs), with a large variety of robust exciton species, represent a versatile platform for investigating the interactions between excitons and a Fermi sea of charges. Recent experiments in charge-tunable monolayer TMDs show robust evidence that the interaction of intralayer excitons with a Fermi sea is best described by exciton–polarons, rather than trions [1-3]. In this work, we report the observation of interlayer (rather than intralayer) exciton (IX) polarons in the low-temperature photoluminescence of a gate-tunable MoSe₂/WSe₂ heterostructure. Increasing electron density leads to a splitting of the neutral IXs peaks into attractive and repulsive IX polaron branches. Interestingly, we observe two species of repulsive polarons in which the exciton carriers located in different layers present parallel and antiparallel alignment. Finally, we investigate the magneto-optical properties of the IX polarons in the Faraday geometry. Our results reveal that, although the attractive polarons show a conventional positive diamagnetic shift, the repulsive polaron branches present anomalous negative diamagnetic shifts.

[1] Phys. Rev. B 95, 035417 (2017)
[2] Nat. Phys. 13, 255 (2017).
[3] Phys. Rev. Lett. 118, 237404 (2017).