Excitons in transition-metal dichalcogenides can be dynamically manipulated using electrostatic fields. Analyzing both in-plane and out-of-plane fields, I compute the exciton Stark shift and electroabsorption spectrum of monolayer $\mathrm{Mo}{\mathrm{S}}_2,\mathrm{MoS}{\mathrm{e}}_2,\mathrm{W}{\mathrm{S}}_2$, and $\mathrm{WS}{\mathrm{e}}_2$. The effect of in-plane fields is found to greatly surpass that of out-of-plane fields. In particular, if exciton binding is reduced through screening by surrounding dielectrics, such as in $\mathrm{Mo}{\mathrm{S}}_2$ encapsulated by hexagonal boron-nitride, the in-plane exciton polarizability exceeds the measured out-of-plane value by nearly two orders of magnitude. Accordingly, pronounced electroabsorption features are expected for fields as low as $10\mathrm{V}\mu {\mathrm{m}}^{-1}$.

• Received 14 June 2016
• Revised 1 August 2016

DOI:https://doi.org/10.1103/PhysRevB.94.125424