Efficient ionization of two dimensional excitons by intense single cycle terahertz pulses

TL;DR

This paper theoretically demonstrates that intense single-cycle terahertz pulses can efficiently ionize excitons in monolayer TMDs, enabling dynamic control of free carriers for optoelectronic applications.

Contribution

It introduces a theoretical framework showing that realistic THz pulses can ionize excitons in TMDs, offering a new method for ultrafast exciton manipulation.

Findings

THz pulses can ionize a significant fraction of excitons in TMDs

Ionization probabilities are experimentally measurable via free carrier absorption

Ionization efficiency varies with dielectric environment and TMD material

Abstract

External electric fields are highly attractive for dynamical manipulation of excitons in two-dimensional materials. Here, we theoretically study the ionization of excitons in monolayer transition metal dichalcogenides (TMDs) by intense pulsed electric fields in the terahertz (THz) regime. We find that THz pulses with realistic field strengths are capable of ionizing a significant fraction of photogenerated excitons in TMDs into free charge carriers. Short THz pulses are therefore an efficient, non-invasive method of dynamically controlling the free carrier concentration in monolayer TMDs, which is useful for applications such as THz modulators. We further demonstrate that exciton ionization probabilities should be experimentally measurable by comparing free carrier absorption before and after the THz pulse. Detailed results are provided for different TMDs in various dielectric environments.