Extended Anharmonic Collapse of Phonon Dispersions in SnS

December 15, 2020
Extended Anharmonic Collapse of Phonon Dispersions in SnS
Phonon dispersion and dynamical susceptibility in SnS measured across the structural transition (Tc=880K). (a), (b) are in the low temperature Pnma phase; (c), (d) are in the high temperature Cmcm phase. (a) and (c) show first principles simulations. Inelastic neutron data collected on (b) CNCS and (d) HB-3. Intensity is plotted on a log10 scale.

Scientific Achievement

An extreme softening of an entire manifold of low energy acoustic and optic phonon branches in observed in warming SnS through a structural transition. 

Significance and Impact

These strong phonon renormalization effects associated with lattice instabilities provide a new mechanism for ultra-low thermal conductivity, a desirable property for thermoelectrics, photovoltaics, and other technologically important materials.

Research Details

  • Inelastic neutron scattering was used to map out the phonon excitation spectra across the structural phase transition.
  • Complementary high-resolution Raman spectra were collected to probe zone-center optical modes.
  • Anharmonic first-principles calculations based on density functional theory were used and to calculate the dynamical susceptibility.

“Extended anharmonic collapse of phonon dispersions in SnS and SnSe,”
Tyson Lanigan-Atkins, S. Yang, Jennifer Niedziela, Dipanshu Bansal, Andrew May, Alexander Puretzky, Jiao Lin, Daniel Pajerowski, Tao Hong, Songxue Chi, Georg Ehlers and Olivier Delaire,
Nature Communications, 11, 4430 (2020). 
DOI: https://doi.org/10.1038/s41467-020-18121-4