We examine anharmonic contributions to the optical phonon modes in bulk Td-MoTe2 through temperature-dependent Raman spectroscopy. At temperatures ranging from 100 K to 200 K, we find that all modes redshift linearly with temperature in agreement with the Gr\"{u}neisen model. However, below 100 K we observe nonlinear temperature-dependent frequency shifts in some modes. We demonstrate that this anharmonic behavior is consistent with the decay of an optical phonon into multiple acoustic phonons. Furthermore, the highest frequency Raman modes show large changes in intensity and linewidth near T≈250 K that correlate well with the Td→1T′ structural phase transition. These results suggest that phonon-phonon interactions can dominate anharmonic contributions at low temperatures in bulk Td-MoTe2, an experimental regime that is currently receiving attention in efforts to understand Weyl semimetals.
@article{arxiv.1606.03050,
title = {Phonon Anharmonicity in Bulk $T_d$-MoTe$_2$},
author = {Jaydeep Joshi and Iris Stone and Ryan Beams and Sergiy Krylyuk and Irina Kalish and Albert Davydov and Patrick Vora},
journal= {arXiv preprint arXiv:1606.03050},
year = {2016}
}