Low temperature vibrational instabilities of MoSe2

This proposal seeks to understand how the lattice dynamics of hexagonal MoSe2 changes with temperature. Inelastic xray scattering (IXS) measurements (beamtime HC-5550), has recenlty revealed for the first time a dramatic softening of the transverse acoustic mode of MoSe2 at the M point upon temperature reduction to 80K, anticipating a structural phase transition. This proposal aims to understand this vibrational instability and observe the phase transition by a combination of diffuse scattering (DS) and IXS extended to 10K. This study will provide a unique insight on the temperature dependence of the transport and optical properties of technologically-relevant transition metal dichalcogenides (TMDs), as controlled by the electron- and exciton- scattering with the zone-boundary acoustic phonons. The prospected results will guide the development of optoelectronic devices based on TMDs two-dimensional crystals.