Charge and Heat Transport in Polycrystalline Metallic Nanostructures

Metals are typically good conductors in which the abilities to transport charge and to transport heat can be related through the Wiedemann--Franz law. Here we report on an abnormal charge and heat transport in polycrystalline metallic nanostructures in which the ability to transport charge is weakened more obviously than that to transport heat. We attribute it to the influence of the internal grain boundaries and have formulated a novel relation to predict the thermal conductivity. The Wiedemann--Franz law is then modified to account for the influence of the grain boundaries on the charge and heat transport with the predictions now agreeing well with the measured results.