We report on room-temperature Raman scattering measurements in few-layer crystals of exfoliated molybdenum ditelluride (MoTe2) performed with the use of 632.8 nm (1.96 eV) laser light excitation. In agreement with a recent study reported by G. Froehlicher et al 1 we observe a complex structure of the out-of-plane vibrational modes (A1g/A 1 ), which can be explained in terms of interlayer interactions between single atomic planes of MoTe2. In the case of low-energy shear and breathing modes of rigid interlayer vibrations, it is shown that their energy evolution with the number of layers can be well reproduced within a linear chain model with only the nearest neighbor interaction taken into account. Based on this model the corresponding in-plane and out-of-plane force constants are determined. We also show that the Raman scattering in MoTe2 measured using 514.5 nm (2.41 eV) laser light excitation results in much simpler spectra. We argue that the rich structure of the out-of-plane vibrational modes observed in Raman scattering spectra excited with the use of 632.8 nm laser light results from its resonance with the electronic transition at the M point of the MoTe2 first Brillouin zone.
We investigate the
origin of emission lines apparent in the low-temperature
photoluminescence spectra of n-doped WS
2
monolayer embedded
in hexagonal BN layers using external magnetic fields and first-principles
calculations. Apart from the neutral A exciton line, all observed
emission lines are related to the negatively charged excitons. Consequently,
we identify emissions due to both the bright (singlet and triplet)
and dark (spin- and momentum-forbidden) negative trions as well as
the phonon replicas of the latter optically inactive complexes. The
semidark trions and negative biexcitons are distinguished. On the
basis of their experimentally extracted and theoretically calculated
g
-factors, we identify three distinct families of emissions
due to exciton complexes in WS
2
: bright, intravalley, and
intervalley dark. The
g
-factors of the spin-split
subbands in both the conduction and valence bands are also determined.
Low temperature and polarization resolved magneto-photoluminescence experiments are used to investigate the properties of dark excitons and dark trions in a monolayer of WS2 encapsulated in hexagonal BN (hBN). We...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.