@article{8e71e28de64944a7b9ea8b22c7d13c8b,
title = "Exciton-Dominated Ultrafast Optical Response in Atomically Thin PtSe2",
abstract = "Strongly bound excitons are a characteristic hallmark of 2D semiconductors, enabling unique light–matter interactions and novel optical applications. Platinum diselenide (PtSe2) is an emerging 2D material with outstanding optical and electrical properties and excellent air stability. Bulk PtSe2 is a semimetal, but its atomically thin form shows a semiconducting phase with the appearance of a band-gap, making one expect strongly bound 2D excitons. However, the excitons in PtSe2 have been barely studied, either experimentally or theoretically. Here, the authors directly observe and theoretically confirm excitons and their ultrafast dynamics in mono-, bi-, and tri-layer PtSe2 single crystals. Steady-state optical microscopy reveals exciton absorption resonances and their thickness dependence, confirmed by first-principles calculations. Ultrafast transient absorption microscopy finds that the exciton dominates the transient broadband response, resulting from strong exciton bleaching and renormalized band-gap-induced exciton shifting. The overall transient spectrum redshifts with increasing thickness as the shrinking band-gap redshifts the exciton resonance. This study provides novel insights into exciton photophysics in platinum dichalcogenides.",
keywords = "excitons, layered two-dimensional materials, platinum diselenide, transient absorption microscopy, ultrafast exciton dynamics",
author = "Seongkwang Bae and Sanghee Nah and Doeon Lee and Muhammad Sajjad and Nirpendra Singh and Kang, {Ku Min} and Sanghoon Kim and Kim, {Geun Ju} and Jaekyun Kim and Hionsuck Baik and Kyusang Lee and Sangwan Sim",
note = "Funding Information: S.B., S.N., D.L., and M.S. contributed equally to this work. The authors thank Sung Bok Seo for assisting with experiments. S.B. and S.S. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (Grant NRF‐2019R1F1A1063457). The TA experiments were carried out with a homebuilt broadband transient absorption microscopy system at the Korea Basic Science Institute (KBSI). S.S. was supported by the Korea Basic Science Institute under the R&D program (Project No. C140440) supervised by the Ministry of Science and ICT. The absorbance experiment was carried out with an ultrawide wavelength range microspectrometer system at the Hanyang University ERICA. M.S and N.S acknowledge the financial support by the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE19‐126. D.L. and K.L. were supported from the US National Science Foundation (NSF) under Grant CMMI‐1825256. This research was funded and conducted, in part, under the Competency Development Program for Industry Specialists of the Korean Ministry of Trade, Industry and Energy (MOTIE), operated by Korea Institute for Advancement of Technology (KIAT) (No. P0002397, HRD program for Industrial Convergence of Wearable Smart Devices). Funding Information: S.B., S.N., D.L., and M.S. contributed equally to this work. The authors thank Sung Bok Seo for assisting with experiments. S.B. and S.S. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (Grant NRF-2019R1F1A1063457). The TA experiments were carried out with a homebuilt broadband transient absorption microscopy system at the Korea Basic Science Institute (KBSI). S.S. was supported by the Korea Basic Science Institute under the R&D program (Project No. C140440) supervised by the Ministry of Science and ICT. The absorbance experiment was carried out with an ultrawide wavelength range microspectrometer system at the Hanyang University ERICA. M.S and N.S acknowledge the financial support by the Abu Dhabi Department of Education and Knowledge (ADEK) under the AARE19-126. D.L. and K.L. were supported from the US National Science Foundation (NSF) under Grant CMMI-1825256. This research was funded and conducted, in part, under the Competency Development Program for Industry Specialists of the Korean Ministry of Trade, Industry and Energy (MOTIE), operated by Korea Institute for Advancement of Technology (KIAT) (No. P0002397, HRD program for Industrial Convergence of Wearable Smart Devices). Publisher Copyright: {\textcopyright} 2021 Wiley-VCH GmbH",
year = "2021",
month = nov,
day = "11",
doi = "10.1002/smll.202103400",
language = "British English",
volume = "17",
journal = "Small",
issn = "1613-6810",
publisher = "Wiley-VCH Verlag",
number = "45",
}