Heat dissipation in atomic-scale junctions

TL;DR

This study investigates heat dissipation in atomic-scale junctions, revealing asymmetric heat flow dependent on electronic transmission characteristics, and introduces experimental techniques to explore thermoelectric effects at the nanoscale.

Contribution

The paper demonstrates the relationship between electronic transmission properties and heat dissipation asymmetry in atomic junctions using novel nanoscale thermocouple probes.

Findings

Heat dissipation is asymmetric in energy-dependent junctions.

Energy-independent junctions show negligible heat dissipation asymmetry.

The techniques enable future studies of Peltier effects and heat transport at the atomic scale.

Abstract

Atomic and single-molecule junctions represent the ultimate limit to the miniaturization of electrical circuits. They are also ideal platforms to test quantum transport theories that are required to describe charge and energy transfer in novel functional nanodevices. Recent work has successfully probed electric and thermoelectric phenomena in atomic-scale junctions. However, heat dissipation and transport in atomic-scale devices remain poorly characterized due to experimental challenges. Here, using custom-fabricated scanning probes with integrated nanoscale thermocouples, we show that heat dissipation in the electrodes of molecular junctions, whose transmission characteristics are strongly dependent on energy, is asymmetric, i.e. unequal and dependent on both the bias polarity and the identity of majority charge carriers (electrons vs. holes). In contrast, atomic junctions whose transmission characteristics show weak energy dependence do not exhibit appreciable asymmetry. Our results unambiguously relate the electronic transmission characteristics of atomic-scale junctions to their heat dissipation properties establishing a framework for understanding heat dissipation in a range of mesoscopic systems where transport is elastic. We anticipate that the techniques established here will enable the study of Peltier effects at the atomic scale, a field that has been barely explored experimentally despite interesting theoretical predictions. Furthermore, the experimental advances described here are also expected to enable the study of heat transport in atomic and molecular junctions, which is an important and challenging scientific and technological goal that has remained elusive.