Quantized thermal conductance in metallic heterojunctions

TL;DR

This study demonstrates quantized thermal and electrical conductance in gold atomic contacts using a novel measurement setup, confirming the Wiedemann-Franz law at the nanoscale and exploring effects of contact size and tip material.

Contribution

It introduces an advanced experimental technique for measuring heat transport in metallic atomic contacts and verifies quantum conductance quantization with different tip materials.

Findings

Thermal conductance quantization observed in gold atomic contacts.

Wiedemann-Franz law confirmed at the atomic scale.

Tip material influences contact stability and measurement success.

Abstract

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.