Urban, J. M.Baranowski, M.Kuc, A.Klopotowski, L.Surrente, A.Ma, Y.Wlodarczyk, D.Suchocki, A.Ovchinnikov, D.Heine, T.Maude, D. K.Kis, A.Plochocka, P.2019-01-232019-01-232019-01-232019-01-0110.1088/2053-1583/aae9b9https://infoscience.epfl.ch/handle/20.500.14299/154008WOS:000449203600003We present a systematic investigation of the electronic properties of bulk and few layer ReS2 van der Waals crystals using low temperature optical spectroscopy. Weak photoluminescence emission is observed from two non-degenerate band edge excitonic transitions separated by similar to 20 meV. The comparable emission intensity of both excitonic transitions is incompatible with a fully thermalized (Boltzmann) distribution of excitons, indicating the hot nature of the emission. While DFT calculations predict bilayer ReS2 to have a direct fundamental band gap, our optical data suggests that the fundamental gap is indirect in all cases.Materials Science, MultidisciplinaryMaterials Scienceres2excitonsdftphotoluminescenceinplane anisotropymonolayer mos2few-layerelectrical-propertiesvalley polarizationdichalcogenide res2crystalsabsorptiontransitionsemiconductorstext::journal::journal article::research article