  A promising route for the development of opto-elelctronic technology is to
use terahertz radiation to modulate the optical properties of semiconductors.
Here we demonstrate the dynamical control of photoluminescence (PL) emission in
few-layer InSe using picosecond terahertz pulses. We observe a strong PL
quenching (up to 50%) after the arrival of the terahertz pulse followed by a
reversible recovery of the emission on the time scale of 50ps at T =10K.
Microscopic calculations reveal that the origin of the photoluminescence
quenching is the terahertz absorption by photo-excited carriers: this leads to
a heating of the carriers and a broadening of their distribution, which reduces
the probability of bimolecular electron-hole recombination and, therefore, the
luminescence. By numerically evaluating the Boltzmann equation, we are able to
clarify the individual roles of optical and acoustic phonons in the subsequent
cooling process. The same PL quenchingmechanismis expected in other van
derWaals semiconductors and the effectwill be particularly strong for materials
with low carrier masses and long carrier relaxation time, which is the case for
InSe. This work gives a solid background for the development of opto-electronic
applications based on InSe, such as THz detectors and optical modulators.
