"Thermal diffusivity above the Mott-Ioffe-Regel limit"

Jiecheng Zhang: Erik D. Kountz, Eli M. Levenson-Falk, Dongjoon Song, Richard L. Greene, and Aharon Kapitulnik; Physical Review B, 12/24/19.

Additional Authors: Erik D. Kountz, Eli M. Levenson-Falk, Dongjoon Song, Richard L. Greene, and Aharon Kapitulnik

Abstract:

We present high-resolution thermal diffusivity measurements on several near optimally doped electron- and hole-doped cuprate systems in a temperature range that passes through the Mott-Ioffe-Regel limit, above which the quasiparticle picture fails. Our primary observations are that the inverse thermal diffusivity is linear in temperature and can be fitted to D−1 Q = aT + b. The slope a is interpreted through the Planckian relaxation time τ ≈ h¯/kBT and a thermal diffusion velocity vB, which is close, but larger than the sound velocity. The intercept b represents a crossover diffusion constant that separates coherent from incoherent quasiparticles. These observations suggest that both phonons and electrons participate in the thermal transport, while reaching the Planckian limit for relaxation time.