Abstract
Strongly anharmonic phonon properties of CuCl are investigated with inelastic neutron-scattering measurements and first-principles simulations. An unusual quasiparticle spectral peak emerges in the phonon density of states with increasing temperature, in both simulations and measurements, emanating from exceptionally strong coupling between conventional phonon modes. Associated with this strong anharmonicity, the lattice thermal conductivity of CuCl is extremely low and exhibits anomalous, nonmonotonic pressure dependence. We show how this behavior arises from the structure of the phonon dispersions augmenting the phase space available for anharmonic three-phonon scattering processes, and contrast this mechanism with common arguments based on negative Grüneisen parameters. These results demonstrate the importance of considering intrinsic phonon-dispersion structure toward understanding scattering processes and designing new ultralow thermal conductivity materials.
Original language | English |
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Article number | 100301 |
Journal | Physical Review B |
Volume | 96 |
Issue number | 10 |
DOIs | |
State | Published - Sep 5 2017 |
Funding
Acknowledgments. S.M. and L.L. acknowledge support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231. S.M. thankfully acknowledges helpful discussions with Prof. Togo regarding phono3py code. Neutron-scattering measurements (D.B., O.D.) were supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, through the Office of Science Early Career Award grant of O.D. (Grant No. DE-SC0016166). The use of Oak Ridge National Laboratory's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. Theoretical work at the University of Missouri was supported by the Department of Energy, Basic Energy Sciences, Computational Materials Science Program through the MAGICS Center, Award No. DE-SC0014607.