The lattice dynamics and high-temperature structural transition in SnS and SnSe are investigated via inelastic neutron scattering, high-resolution Raman spectroscopy and anharmonic first-principles simulations. We uncover a spectacular, extreme softening and reconstruction of an entire manifold of low-energy acoustic and optic branches across a structural transition, reflecting strong directionality in bonding strength and anharmonicity. Further, our results solve a prior controversy by revealing the soft-mode mechanism of the phase transition that impacts thermal transport and thermoelectric efficiency. Our simulations of anharmonic phonon renormalization go beyond low-order perturbation theory and capture these striking effects, showing that the large phonon shifts directly affect the thermal conductivity by altering both the phonon scattering phase space and the group velocities. These results provide a detailed microscopic understanding of phase stability and thermal transport in technologically important materials, providing further insights on ways to control phonon propagation in thermoelectrics, photovoltaics, and other materials requiring thermal management.
Lanigan-Atkins, Tyson, Yang, S., Niedziela, Jennifer L., Bansal, Dipanshu, May, Andrew F., Puretzky, Alexander A., Lin, Jiao Y., Pajerowski, Daniel M., Hong, Tao, Chi, Songxue, Ehlers, Georg, & Delaire, O. (2020). Extended anharmonic collapse of phonon dispersions in SnS and SnSe. Nature Communications, 11(1). https://doi.org/10.1038/s41467-020-18121-4
@article{osti_1659620,
author = {Lanigan-Atkins, Tyson and Yang, S. and Niedziela, Jennifer L. and Bansal, Dipanshu and May, Andrew F. and Puretzky, Alexander A. and Lin, Jiao Y. and Pajerowski, Daniel M. and Hong, Tao and Chi, Songxue and others},
title = {Extended anharmonic collapse of phonon dispersions in SnS and SnSe},
annote = {The lattice dynamics and high-temperature structural transition in SnS and SnSe are investigated via inelastic neutron scattering, high-resolution Raman spectroscopy and anharmonic first-principles simulations. We uncover a spectacular, extreme softening and reconstruction of an entire manifold of low-energy acoustic and optic branches across a structural transition, reflecting strong directionality in bonding strength and anharmonicity. Further, our results solve a prior controversy by revealing the soft-mode mechanism of the phase transition that impacts thermal transport and thermoelectric efficiency. Our simulations of anharmonic phonon renormalization go beyond low-order perturbation theory and capture these striking effects, showing that the large phonon shifts directly affect the thermal conductivity by altering both the phonon scattering phase space and the group velocities. These results provide a detailed microscopic understanding of phase stability and thermal transport in technologically important materials, providing further insights on ways to control phonon propagation in thermoelectrics, photovoltaics, and other materials requiring thermal management.},
doi = {10.1038/s41467-020-18121-4},
url = {https://www.osti.gov/biblio/1659620},
journal = {Nature Communications},
issn = {ISSN 2041-1723},
number = {1},
volume = {11},
place = {United States},
publisher = {Nature Publishing Group},
year = {2020},
month = {09}}
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS), High Flux Isotope Reactor (HFIR), and Center for Nanophase Materials Science (CNMS); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
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