11 Thermal Transport by Phonons

Learning Objectives

State Fourier’s law for heat transport in solids and define thermal diffusivity.
Derive the kinetic-theory expression for lattice thermal conductivity from a phonon picture.
Distinguish boundary, defect, isotope/alloy, normal, and umklapp scattering mechanisms.
Use Matthiessen’s rule to discuss regimes and crossover scales in \(\kappa(T)\).
Explain why crystalline insulators typically show a low-temperature peak in \(\kappa(T)\), whereas glasses often show a plateau.