  Achieving fully tunable quantum confinement of excitons has been a
long-standing goal in optoelectronics and quantum photonics. We demonstrate
electrically controlled 1D quantum confinement of neutral excitons by means of
a lateral p-i-n junction in a monolayer transition metal dichalcogenide
semiconductor. Exciton trapping in the i-region occurs due to the dc Stark
effect induced by in-plane electric fields. Remarkably, we observe a new
confinement mechanism arising from the repulsive polaronic dressing of excitons
by electrons and holes in the surrounding regions. The overall confinement
potential leads to quantization of excitonic motion, which manifests in the
emergence of multiple spectrally narrow, voltage-dependent resonances in
reflectance and photoluminescence measurements. Additionally, the
photoluminescence from confined excitonic states exhibits high degree of linear
polarization, highlighting the 1D nature of quantum confinement. Electrically
tunable quantum confined excitons may provide a scalable platform for arrays of
identical single photon sources and constitute building blocks of strongly
correlated photonic many-body systems.
