Efficiency bounds on thermoelectric transport in magnetic fields: The role of inelastic processes

TL;DR

This paper investigates how breaking time-reversal symmetry and inelastic processes in a thermoelectric device can enhance efficiency bounds, potentially approaching Carnot efficiency but with trade-offs in power output.

Contribution

It introduces a model of a three-terminal thermoelectric device with magnetic fields and inelastic processes, deriving bounds on efficiency and power.

Findings

Breaking time-reversal symmetry can increase the figure of merit.

Efficiency at maximum power can approach Carnot efficiency.

Electric power diminishes as efficiency nears Carnot limit.

Abstract

We examine the efficiency of an effective two-terminal thermoelectric device under broken time-reversal symmetry. The setup is derived from a three-terminal thermoelectric device comprising a thermal terminal and two electronic contacts, under a magnetic field. We find that breaking time-reversal symmetry in the presence of the inelastic electron-phonon processes can significantly enhance the figure of merit for delivering electric power by supplying heat from a phonon bath, beyond the one for producing the electric power by investing thermal power from the electronic heat current. The efficiency of such a device is bounded by the non-negativity of the entropy production of the original three-terminal junction. The efficiency at maximal power can be quite close to the Carnot efficiency, but then the electric power vanishes.