paper

Revealing exciton masses and dielectric properties of monolayer semiconductors with high magnetic fields

arXiv:1904.03238 · doi:10.1038/s41467-019-12180-y

Abstract

In semiconductor physics, many essential optoelectronic material parameters can be experimentally revealed via optical spectroscopy in sufficiently large magnetic fields. For monolayer transition-metal dichalcogenide semiconductors, this field scale is substantial --tens of teslas or more-- due to heavy carrier masses and huge exciton binding energies. Here we report absorption spectroscopy of monolayer MoS $_{2}$ , MoSe $_{2}$ , MoTe $_{2}$ , and WS $_{2}$ in very high magnetic fields to 91~T. We follow the diamagnetic shifts and valley Zeeman splittings of not only the exciton's $1 s$ ground state but also its excited $2 s$ , $3 s$ , ..., $n s$ Rydberg states. This provides a direct experimental measure of the effective (reduced) exciton masses and dielectric properties. Exciton binding energies, exciton radii, and free-particle bandgaps are also determined. The measured exciton masses are heavier than theoretically predicted, especially for Mo-based monolayers. These results provide essential and quantitative parameters for the rational design of opto-electronic van der Waals heterostructures incorporating 2D semiconductors.

updated; now also including data on MoTe2. Accepted & in press, Nature Commun