Strong bounds on Onsager coefficients and efficiency for three terminal thermoelectric transport in a magnetic field

TL;DR

This paper establishes fundamental bounds on Onsager coefficients and efficiency limits for three-terminal thermoelectric devices under magnetic fields, highlighting the impact of asymmetry and reversible currents.

Contribution

It derives new bounds on Onsager coefficients and efficiency in three-terminal thermoelectric systems with broken time-reversal symmetry, emphasizing the role of current conservation.

Findings

Maximum efficiency is limited to  of Carnot efficiency under strong asymmetry.

Efficiency at maximum power can exceed Curzon-Ahlborn limit  of Carnot.

Standard entropy production analysis is incomplete without considering current conservation.

Abstract

For thermoelectric transport in the presence of a magnetic field that breaks time-reversal symmetry, a strong bound on the Onsager coefficients is derived within a general set-up using three terminals. Asymmetric Onsager coefficients lead to a maximum efficiency substantially smaller than the Carnot efficiency reaching only \eta_C/4 in the limit of strong asymmetry. Related bounds are derived for efficiency at maximum power, which can become larger than the Curzon-Ahlborn value \eta_C/2, and for a cooling device. Our approach reveals that in the presence of reversible currents the standard analysis based on the positivity of entropy production is incomplete without considering the role of current conservation explicitly.