Controlling exciton many-body states by the electric-field effect in monolayer MoS2

We report magneto-optical spectroscopy of gated monolayer MoS2 in high magnetic fields up to 28 T and obtain new insights on the many-body interaction of neutral and charged excitons with the resident charges of distinct spin and valley texture. For neutral excitons at low electron doping, we observe a nonlinear valley Zeeman shift due to dipolar spin-interactions that depends sensitively on the local carrier concentration. As the Fermi energy increases to dominate over the other relevant energy scales in the system, the magneto-optical response depends on the occupation of the fully spin-polarized Landau levels (LL) in both K/K' valleys. This manifests itself in a many-body state. Our experiments demonstrate that the exciton in monolayer semiconductors is only a single particle boson close to charge neutrality. We find that away from charge neutrality it smoothly transitions into polaronic states with a distinct spin-valley flavor that is defined by the LL quantized spin and valley texture.

Automated summary

In this study, magneto-optical spectroscopy of gated monolayer MoS2 was conducted in high magnetic fields, revealing insights into the interaction of neutral and charged excitons with distinct spin and valley textures. It was found that at low electron doping, neutral excitons exhibit a nonlinear valley Zeeman shift dependent on local carrier concentration, transitioning smoothly into polaronic states away from charge neutrality. The experiments demonstrate that excitons in monolayer semiconductors behave as single particle bosons close to charge neutrality, affected by the quantized spin and valley textures of Landau levels in the system.