Thermopower of atomic-size metallic contacts

TL;DR

This study measures the thermopower and conductance of atomic-scale metallic contacts, revealing abrupt changes and quantum interference effects that influence thermopower behavior at atomic dimensions.

Contribution

It provides the first simultaneous measurement of thermopower and conductance at atomic scale and introduces a quantum interference model to explain observed phenomena.

Findings

Thermopower exhibits abrupt steps coinciding with conductance jumps.

Thermopower distribution is random, positive or negative, around large contact values.

Thermopower is suppressed at the quantum conductance G_0 = 2e^2/h.

Abstract

The thermopower and conductance of atomic-size metallic contacts have been simultaneously measured using a mechanically controllable break junction. For contacts approaching atomic dimensions, abrupt steps in the thermopower are observed which coincide with jumps in the conductance. The measured thermopower for a large number of atomic-size contacts is randomly distributed around the value for large contacts and can be either positive or negative in sign. However, it is suppressed at the quantum value of the conductance G_0 = 2e^2/h. We derive an expression that describes these results in terms of quantum interference of electrons backscattered in the banks.