Time-dependent thermoelectric transport for nanoscale thermal machines

TL;DR

This paper investigates the effects of time-dependent coupling modulations on nanoscale thermoelectric transport, providing new theoretical expressions and demonstrating applications in cyclic refrigeration with transient current analysis.

Contribution

It introduces energy and heat current expressions for time-dependent lead-dot couplings and applies them to design a nanoscale refrigerator, addressing strong coupling energy flow ambiguities.

Findings

Transient currents occur during fast lead-dot coupling modulation.

Theoretical framework uses Keldysh nonequilibrium Green's functions.

Design of a cyclic refrigerator exploiting time-dependent couplings.

Abstract

We analyze an electronic nanoscale thermal machine driven by time-dependent environment: besides bias and gate voltage variations, we consider also the less prevailing time modulation of the couplings between leads and dot. We provide energy and heat current expressions in such situations, as well as expressions for the power exchanged between the dot+leads system and its outside. Calculations are made in the Keldysh nonequilibrium Green's function framework. We apply these results to design a cyclic refrigerator, circumventing the ambiguity of defining energy flows between subsystems in the case of strong coupling. For fast lead-dot coupling modulation, we observe transient currents which cannot be ascribed to charge tunneling.