Among Transition Metal Dichalcogenides (TMD), NbS2 is often considered as the archetypal compound that does not have a Charge Density Wave (CDW) in any of its polytypes. By comparison, close iso-electronic compounds such as NbSe2, TaS2 and TaSe2 all have CDW in at least one polytype. Here, we report traces of CDW in the 2H polytype of NbS2, using diffuse x-ray scattering measurements at 77\,K and room temperature. We observe 12 extremely weak satellite peaks located at ±13o 54' from a∗ and b∗ around each Bragg peaks in the (h,k,0) plane. These satellite peaks are commensurate with the lattice via 3q−q′=a∗, where q′ is the 120∘ rotation of q, and define two chiral 13a×13a superlattices in real space. These commensurate wavevectors and tilt angle are identical to those of the CDW observed in the 1T polytype of TaS2 and TaSe2. To understand this similarity and the faintness of the peaks, we discuss possible sources of local 1T polytype environment in bulk 2H-NbS2 crystals.
@article{arxiv.1801.08617,
title = {Traces of Charge Density Waves in NbS$_2$},
author = {Maxime Leroux and Laurent Cario and Alexei Bosak and Pierre Rodière},
journal= {arXiv preprint arXiv:1801.08617},
year = {2018}
}