  To develop next-generation electronics and high efficiency energy-harvesting
devices, it is crucial to understand how charge and heat are transported at the
nanoscale. Metallic atomic-size contacts are ideal systems to probe the quantum
limits of transport. The thermal and electrical conductance of gold atomic
contacts has been recently proven to be quantized at room temperature. However,
a big experimental challenge in such measurements is represented by the fast
breaking dynamics of metallic junctions at room temperature, which can exceed
the typical response time of the thermal measurement. Here we use a
break-junction setup that combines Scanning Tunneling Microscopy with suspended
micro electro-mechanical systems with a gold-covered membrane and an integrated
heater acting also as thermometer. By using other metals as tip materials,
namely Pt, PtIr and W, we show heat transport measurements through single gold
atomic contacts. The dependence of the thermal conductance is analysed as
function of contact size and material used. We find that by using Pt and Pt-Ir
tips we can maximize the mechanical stability and probability of forming single
Au atomic contacts. We then show the quantization of the electrical and thermal
conductance with the verification of the Wiedemann-Franz law at the atomic
scale. We expect these findings to increase the flexibility of experimental
techniques probing heat transport in metallic quantum point contacts and to
enable the investigation of thermal properties of molecular junctions.
