Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe <inf>2</inf>
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© 2018, The Author(s), under exclusive licence to Springer Nature Limited. Superionic crystals exhibit ionic mobilities comparable to liquids while maintaining a periodic crystalline lattice. The atomic dynamics leading to large ionic mobility have long been debated. A central question is whether phonon quasiparticles—which conduct heat in regular solids—survive in the superionic state, where a large fraction of the system exhibits liquid-like behaviour. Here we present the results of energy- and momentum-resolved scattering studies combined with first-principles calculations and show that in the superionic phase of CuCrSe 2 , long-wavelength acoustic phonons capable of heat conduction remain largely intact, whereas specific phonon quasiparticles dominated by the Cu ions break down as a result of anharmonicity and disorder. The weak bonding and large anharmonicity of the Cu sublattice are present already in the normal ordered state, resulting in low thermal conductivity even below the superionic transition. These results demonstrate that anharmonic phonon dynamics are at the origin of low thermal conductivity and superionicity in this class of materials.
SubjectScience & Technology
Published Version (Please cite this version)10.1038/s41567-018-0298-2
Publication InfoNiedziela, JL; Bansal, D; May, AF; Ding, J; Lanigan-Atkins, T; Ehlers, G; ... Delaire, O (2019). Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe <inf>2</inf>. Nature Physics, 15(1). pp. 73-78. 10.1038/s41567-018-0298-2. Retrieved from https://hdl.handle.net/10161/20065.
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Associate Professor of Mechanical Engineering and Materials Science
Olivier Delaire's research program investigates atomistic transport processes of energy and charge, and thermodynamics in energy materials. The nanoscale studies probe atomic dynamics and elementary excitations in condensed-matter systems (phonons, electrons, spins), their couplings and their effects on macroscopic material properties. Current materials of interest include thermoelectrics, ferroelectrics/multiferroics, spin-caloritronics, and photovoltaics. The Delaire group develops new meth