Interplay between many body effects and Coulomb screening in the optical bandgap of atomically thin MoS2

• Published in: Nanoscale Vol. 9; no. 30; pp. 10647 - 10652
• Main Authors: Park, Youngsin, Han, Sang Wook, Chan, Christopher C S, Reid, Benjamin P L, Taylor, Robert A, Kim, Nammee, Jo, Yongcheol, Im, Hyunsik, Kim, Kwang S
• Format: Journal Article
• Language: English
• Published: 14.08.2017
• ISSN: 2040-3372
• DOI: 10.1039/c7nr01834g

Due to its unique layer-number dependent electronic band structure and strong excitonic features, atomically thin MoS2 is an ideal 2D system where intriguing photoexcited-carrier-induced phenomena can be detected in excitonic luminescence. We perform micro-photoluminescence (PL) measurements and observe that the PL peak redshifts nonlinearly in mono- and bi-layer MoS2 as the excitation power is increased. The excited carrier-induced optical bandgap shrinkage is found to be proportional to n4/3, where n is the optically-induced free carrier density. The large exponent value of 4/3 is explicitly distinguished from a typical value of 1/3 in various semiconductor quantum well systems. The peculiar n4/3 dependent optical bandgap redshift may be due to the interplay between bandgap renormalization and reduced exciton binding energy.