Strong interactions between excitons are a characteristic feature of two-dimensional (2D) semiconductors, determining important excitonic properties, such as exciton lifetime, coherence, and photon-emission efficiency. Rhenium disulfide (ReS2), a member of the 2D transition-metal dichalcogenide (TMD) family, has recently attracted great attention due to its unique excitons that exhibit excellent polarization selectivity and coherence features. However, an in-depth understanding of exciton-exciton interactions in ReS2 is still lacking. Here we used ultrafast pump-probe spectroscopy to study exciton-exciton interactions in monolayer (1L), bilayer (2L), and triple layer ReS2. We directly measure the rate of exciton-exciton annihilation, a representative Auger-type interaction between excitons. It decreases with increasing layer number, as observed in other 2D TMDs. However, while other TMDs exhibit a sharp weakening of exciton-exciton annihilation between 1L and 2L, such behavior was not observed in ReS2. We attribute this distinct feature in ReS2 to the relatively weak interlayer coupling, which prohibits a substantial change in the electronic structure when the thickness varies. This work not only highlights the unique excitonic properties of ReS2 but also provides novel insight into the thickness dependence of exciton-exciton interactions in 2D systems.
Bibliographical noteFunding Information:
S.S. was supported by the NRF through the government of Korea (MSIP) (Grant NRF-2019R1F1A1063457) and the Korea Basic Science Institute under the R&D program (Project No. C030440) supervised by the Ministry of Science and ICT. J.L., M.C., W.H., and H.C. were supported by the NRF through the government of Korea (MSIP) (Grant No. 2018R1A2A1A05079060, the Creative Materials Discovery Program (Grant No. 2017M3D1A1040828), and the Institute for Basic Science (IBS) (Korea under Project Code IBS-R014-G1-2018-A1), and Scalable Quantum Computer Technology Platform Center (Grant 2019R1A5A1027055). D.L. and K.L. were supported from the U.S. National Science Foundation (NSF) under Grant CMMI-1825256. M.-H.J. and S.C. were supported by the Institute for Basic Science (IBS), Korea (project code IBS-R014-A1). This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Los Alamos National Laboratory and Sandia National Laboratories, and was also supported by the LANL LDRD program.
© 2020 American Physical Society.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics