Extended anharmonic collapse of phonon dispersions in SnS and SnSe

T. Lanigan-Atkins, S. Yang, J. L. Niedziela, D. Bansal, A. F. May, A. A. Puretzky, J. Y.Y. Lin, D. M. Pajerowski, T. Hong, S. Chi, G. Ehlers, O. Delaire

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Abstract

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.

Original languageEnglish
Article number4430
JournalNature Communications
Volume11
Issue number1
DOIs
StatePublished - Dec 1 2020

Funding

We thank Olle Hellman for providing access to and support with the TDEP software package. We thank Jason Craig at ORNL for sample encapsulation, and Rebecca Mills at ORNL for help with neutron furnaces. We thank Chen Li for help with initial screening of SnS crystals. Neutron scattering data collection and analysis by TLA and OD was supported the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Award No. DE-SC0019299. First-principles simulations (SY) and neutron data collection (JN, DB) were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under the Early Career Award No. DE-SC0016166. Sample synthesis (AFM) was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The use of Oak Ridge National Laboratory’s Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. DOE. Theoretical calculations were performed using resources of the National Energy Research Scientific Computing Center, a U. S. DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Initial Raman scattering measurements were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

FundersFunder number
Scientific User Facilities Division
U.S. Department of Energy
Office of ScienceDE-AC02-05CH11231
Basic Energy Sciences
Oak Ridge National Laboratory
Division of Materials Sciences and EngineeringDE-SC0019299, DE-SC0016166

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