Many-particle induced band renormalization processes in few- and mono-layer MoS2

Yuan-Yuan Yue; Zhuo Wang; Lei Wang; Hai-Yu Wang; Yang Chen; Dan Wang; Qi-Dai Chen; Bing-Rong Gao; Andrew T S Wee; Cheng-Wei Qiu; Hong-Bo Sun

doi:10.1088/1361-6528/abcfec

Many-particle induced band renormalization processes in few- and mono-layer MoS₂

Nanotechnology. 2021 Jan 8;32(13). doi: 10.1088/1361-6528/abcfec.

Authors

Yuan-Yuan Yue¹, Zhuo Wang², Lei Wang^{1

3}, Hai-Yu Wang¹, Yang Chen¹, Dan Wang¹, Qi-Dai Chen¹, Bing-Rong Gao¹, Andrew T S Wee⁴, Cheng-Wei Qiu³, Hong-Bo Sun⁵

Affiliations

¹ State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, People's Republic of China.
² International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, People's Republic of China.
³ Department of Electrical & Computer Engineering, National University of Singapore, Singapore 117583, Singapore.
⁴ Department of Physics, National University of Singapore, Singapore 117542, Singapore.
⁵ State Key Laboratory of Precision Measurement and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, People's Republic of China.

PMID: 33427201
DOI: 10.1088/1361-6528/abcfec

Abstract

Band renormalization effects play a significant role for two-dimensional (2D) materials in designing a device structure and customizing their optoelectronic performance. However, the intrinsic physical mechanism about the influence of these effects cannot be revealed by general steady-state studies. Here, band renormalization effects in organic superacid treated monolayer MoS₂, untreated monolayer MoS₂and few-layer MoS₂are quantitatively analyzed by using broadband femtosecond transient absorption spectroscopy. In comparison with the untreated monolayer, organic superacid treated monolayer MoS₂maintains a direct bandgap structure with two thirds of carriers populated at K valley, even when the initial exciton density is as high as 2.05 × 10¹⁴cm^-2(under 400 nm excitations). While for untreated monolayer and few-layer MoS₂, many-particle induced band renormalizations lead to a stronger imbalance for the carrier population between K and Q valleys inkspace, and the former experiences a direct-to-indirect bandgap transition when the initial exciton density exceeds 5.0 × 10¹³cm^-2(under 400 nm excitations). Those many-particle induced band renormalization processes further suggest a band-structure-controlling method in practical 2D devices.

Keywords: band renormalization; broadband femtosecond transient absorption; direct-to-indirect bandgap transition; monolayer MoS2; organic superacid treatment.