Electrically tunable Rydberg series excitonic and trionic luminescence in monolayer MoTe₂

Abstract

Non-hydrogenic Rydberg series associated with excitons have been identified in ultraclean monolayer TMDCs. Here, we investigated the radiative properties of the excitonic Rydberg series in monolayer MoTe₂ based devices and the influence of Fermi level position on the same. Using low temperature (4K) photoluminescence measurements, we observed bright emission from the first three states of the excitonic Rydberg series, namely A1s, 2s and 3s. Upon doping on either electron or hole side, oscillator strengths are rapidly transferred to the corresponding trion (charged exciton/attractive polaron) states associated with the aforementioned neutral excitonic resonances. Energy shifts between different states are observed as a function of gate voltage, indicating strong band-structure renormalization. Our work identifies MoTe₂ as a novel platform to realize highly tunable bright light sources or electro-optic modulators in the NIR.