Using a semiclassical approach, we derive a fully analytical expression for the ionization rate of excitons in two-dimensional materials due to an external static electric field, which eliminates the need for complicated numerical calculations. Our formula shows quantitative agreement with more sophisticated numerical methods based on the exterior complex scaling approach, which solves a non-Hermitian eigenvalue problem yielding complex energy eigenvalues, where the imaginary part describes the ionization rate. Results for excitons in hexagonal boron nitride and the $A$ exciton in transition metal dichalcogenides are given as simple examples. The extension of the theory to include spin-orbit-split excitons in transition metal dichalcogenides is trivial.

• Received 30 April 2020
• Revised 18 June 2020
• Accepted 22 June 2020

DOI:https://doi.org/10.1103/PhysRevB.102.035402