Phonon transport in gold quantum wires: temperature and thickness dependence

We investigated phonon contributions to nanoscale thermal transport in gold nanowires exhibiting quantized electrical conductance. Nanowires with varying thicknesses were fabricated, and the thermal conductance of each nanowire was measured as a function of temperature. The thermal conductance exhibits an approximately linear temperature dependence for all samples, which is consistent with electron-dominated heat transport. The phonon contribution was estimated by subtracting the electronic component calculated using the Wiedemann-Franz law. The results indicate that phonon transport in nanowires is governed by competing scattering mechanisms. At low temperatures, suppressed phonon scattering leads to a nearly ballistic transport regime that is dominated by size-dependent boundary scattering. In contrast, at higher temperatures, Umklapp scattering becomes dominant, resulting in bulk-like phonon transport even at the nanoscale. These findings provide direct experimental insights into phonon transport in metallic nanowires. This study establishes that conventional phonon transport mechanisms remain valid even in the quantum wire regime.