Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides

TL;DR

This paper demonstrates room temperature terahertz electroabsorption modulation in monolayer transition metal dichalcogenides, revealing a new Franz-Keldysh effect manifestation that enables efficient, high-speed optoelectronic devices.

Contribution

It uncovers a novel THz-induced Franz-Keldysh effect on excitons in monolayer MoS₂, enabling large modulation depths at room temperature for potential high-speed applications.

Findings

THz pump modifies exciton coherence lifetime without changing oscillator strength or peak energy.

Achieves electroabsorption modulation depth of 0.05 dB/nm at room temperature.

Reveals a new manifestation of the Franz-Keldysh effect on excitons.

Abstract

The interaction between off-resonant laser pulses and excitons in monolayer transition metal dichalcogenides is attracting increasing interest as a route for the valley-selective coherent control of the exciton properties. Here, we extend the classification of the known off-resonant phenomena by unveiling the impact of a strong THz field on the excitonic resonances of monolayer MoS$_2$. We observe that the THz pump pulse causes a selective modification of the coherence lifetime of the excitons, while keeping their oscillator strength and peak energy unchanged. We rationalize these results theoretically by invoking a hitherto unobserved manifestation of the Franz-Keldysh effect on an exciton resonance. As the modulation depth of the optical absorption reaches values as large as 0.05 dB/nm at room temperature, our findings open the way to the use of semiconducting transition metal dichalcogenides as compact and efficient platforms for high-speed electroabsorption devices.