Seebeck effect at the atomic scale

TL;DR

This paper investigates the atomic-scale Seebeck effect, revealing how coherent electron and heat transport at the nanoscale relates thermoelectric signals to atomic wavefunctions and local density of states, with implications for thermoelectric imaging.

Contribution

It introduces a mesoscopic Seebeck coefficient model linked to local density of states and proposes a simulation method for thermoelectric imaging at the atomic scale.

Findings

Atomic Seebeck effect is driven by coherent electron and heat transport.

The mesoscopic Seebeck coefficient relates to the energy derivative of local density of states.

Simulation successfully identified a defect in graphene through thermoelectric imaging.

Abstract

The atomic variations of electronic wavefunctions at the surface and electron scattering near a defect have been detected unprecedentedly by tracing thermoelectric voltages given a temperature bias [Cho et al., Nature Mater. 12, 913 (2013)]. Because thermoelectricity, or Seebeck effect, is associated with heat-induced electron diffusion, how the thermoelectric signal is related to the atomic-scale wavefunctions and what the role of the temperature is at such a length scale remain very unclear. Here we show that coherent electron and heat transport through a point-like contact produces an atomic Seebeck effect, which is described by mesoscopic Seebeck coefficient multiplied with an effective temperature drop at the interface. The mesoscopic Seebeck coefficient is approximately proportional to the logarithmic energy derivative of local density of states at the Fermi energy. We deduced that the effective temperature drop at the tip-sample junction could vary at a sub-angstrom scale depending on atom-to-atom interaction at the interface. A computer-based simulation method of thermoelectric images is proposed, and a point defect in graphene was identified by comparing experiment and the simulation of thermoelectric imaging.