New Nature Physics paper on anharmonic phonons in superionic CuCrSe2

October 8, 2018

Our paper investigating anharmonic phonons in CuCrSe2 with inelastic neutron and x-ray scattering and first-principles simulations is now online in Nature Physics:

Congratulations to all Delaire group members and collaborators for the great work!

"Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe2"

Jennifer L. Niedziela, Dipanshu Bansal, Andrew F. May, Jingxuan Ding, Tyson Lanigan-Atkins, Georg Ehlers, Douglas L. Abernathy, Ayman Said & Olivier Delaire

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 CuCrSe2, 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.