Neutron scattering and atomic dynamics simulations reveal that complex crystals can conduct heat like a glass through diffusive quantum hopping. The revealed strategies will enable the down-tuning of amorphous-like heat conductivity for energy conversion and thermal barriers, unlocking untapped efficiencies.
A crossover in conduction from the conventional phonon-gas channel to the unusual diffuson channel occurs near room temperature in Yb14MnSb11, a complex Zintl phase. Researchers used a recently developed framework which quantifies how mode overlap enables heat conduction through the diffuson channel – diffusive quantum energy hopping. Within the diffuson channel, vibrational energy diffuses in a random walk, in contrast to the phonon-gas channel where energy propagates in wave-packets. Inelastic neutron scattering reveals the extent of mode overlap and validates lattice dynamics calculations. The authors establish that the diffuson channel can be down-tuned by controlling mode overlap through crystal chemistry and varying the atomic masses.