Designer thermal switches: Effect of the contact material on instantaneous thermoelectric transport through a strongly interacting quantum dot

TL;DR

This paper studies how contact material affects the immediate thermoelectric response of a quantum dot in the Kondo regime, revealing oscillations influenced by contact density of states and temperature.

Contribution

It demonstrates the impact of contact geometry and material on thermoelectric oscillations in quantum dots, highlighting graphene's advantages over metals.

Findings

Thermopower oscillates sinusoidally with frequency related to contact density of states.

Oscillation amplitude increases as temperature decreases, saturating near the Kondo temperature.

Graphene contacts reduce oscillations, making them preferable for quantum dot thermoelectric applications.

Abstract

We investigate the effect of contact geometry on the instantaneous thermoelectric response of a quantum dot pushed suddenly into the Kondo regime via a gate voltage using time dependent non-crossing approximation and linear response Onsager relations. We utilize graphene and metal contacts for this purpose. Instantaneous thermopower displays sinusoidal oscillations whose frequency is proportional to the energy separation between the van Hove singularity in the contact density of states and Fermi level for both cases regardless of the asymmetry factor at the onset of Kondo timescale. The amplitude of the oscillations increases with decreasing temperature saturating around the Kondo temperature. We also calculate the instantaneous figure of merit and show that the oscillations taking place at temperatures above the Kondo temperature are enhanced more than the ones occurring at lower temperatures due to the violation of the Wiedemann-Franz law. Graphene emerges as a more promising electrode candidate than ordinary metals in single electron devices since it can minimize these oscillations.