Controlling the thermoelectric effect by mechanical manipulation of the electron's quantum phase in atomic junctions

TL;DR

This paper demonstrates that mechanical deformation of atomic junctions can reversibly control the magnitude and sign of thermoelectric voltage by tuning quantum interference effects, combining experimental and theoretical insights.

Contribution

It introduces a method to reversibly manipulate thermoelectric voltage in atomic junctions through mechanical strain, revealing quantum interference as a key control mechanism.

Findings

Mechanical strain switches thermoelectric voltage sign.

Quantum interference tuning alters electronic transport resonances.

Atomic junctions exhibit both positive and negative thermoelectric voltages on demand.

Abstract

The thermoelectric voltage developed across an atomic metal junction (i.e., a nanostructure in which one or a few atoms connect two metal electrodes) in response to a temperature difference between the electrodes, results from the quantum interference of electrons that pass through the junction multiple times after being scattered by the surrounding defects. Here we report successfully tuning this quantum interference and thus controlling the magnitude and sign of the thermoelectric voltage by applying a mechanical force that deforms the junction. The observed switching of the thermoelectric voltage is reversible and can be cycled many times. Our ab initio and semi-empirical calculations elucidate the detailed mechanism by which the quantum interference is tuned. We show that the applied strain alters the quantum phases of electrons passing through the narrowest part of the junction and hence modifies the electronic quantum interference in the device. Tuning the quantum interference causes the energies of electronic transport resonances to shift, which affects the thermoelectric voltage. These experimental and theoretical studies reveal that Au atomic junctions can be made to exhibit both positive and negative thermoelectric voltages on demand, and demonstrate the importance and tunability of the quantum interference effect in the atomic-scale metal nanostructures.