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WSSe Monolayers as a New Darkish Material
* 1 , 2 , 2 , 1 , 3 , 3 , 3 , 4 , 5 , 1 , 2 , 1
1  Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
2  Physics Department, Sapienza University of Rome, p.le Aldo Moro 2, 00185 Rome, Italy
3  Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
4  Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
5  International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
Academic Editor: Antonio Di Bartolomeo

Published: 24 April 2022 by MDPI in 3rd International Online-Conference on Nanomaterials session Poster

Monolayers of transition metal dichalcogenides (TMD) are direct bandgap semiconductors in which optical and spin properties are dominated by the formation of bound electron-hole pairs, excitons. Alloys of TDMS have emerged as materials with tunable electronic structures, effective masses of carriers, and valley polarization with various alloy compositions. In this work we investigate the low-temperature photoluminescence spectra of WSSe monolayer embedded in hexagonal boron nitride (hBN) layers using external magnetic fields. On this basis we extract g-factors which help us to distinguish excitonic complexes. Additionally, we study PL spectra in the function of laser power and temperature. Based on these experiments we identify emissions due to bright (exciton and trion) transitions and dark (negative trion) transition. WSSe is comparable to WS2 and WSe2 so-called „darkish” materials, in which the excitonic ground state is optically inactive. The energy range of emission lines which correspond to excitionic complexes apparent in WSSe is similar to WS2 and WSe2. These two materials are known for their excellent valley polarisation due to the strong spin−orbit coupling and WSSe is expected to be the same.

Keywords: transition metal dichalcogenides, monolayers, WSSe, excitons, photoluminescence, g-factor