Two-photon absorption and subband photodetection in monolayer MoS₂

We develop a theoretical model to quantify the two-photon absorption (2 PA) coefficients of monolayer MoS₂. Based on two-dimensional excitons, our model reveals the 2 PA coefficient spectrum on the order of 0.01-0.1 cm/MW in the near-infrared for monolayer MoS₂. As compared to the band theory for bulk semiconductors, these coefficients are enhanced by at least one order of magnitude. Our model is in agreement with light-intensity-dependent photocurrent measurements on a monolayer MoS₂, subband photodetector with femtosecond laser pulses.