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Interplay between many body effects and Coulomb screening in the optical bandgap of atomically thin MoS2
Youngsin Park1, Sang Wook Han, Christopher C S Chan
1Department of Chemistry and Physics, School of Natural Science, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea. kimks@unist.ac.kr.
Abstract:
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.
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