Unconventional four-terminal thermoelectric transport due to inelastic transport: Cooling by transverse heat current, transverse thermoelectric effect, and Maxwell demon

We show that, in mesoscopic four-terminal thermoelectric devices with two electrodes (the source and the drain) and two heat baths, inelastic-scattering processes can lead to unconventional thermoelectric transport. The source (or the drain) can be cooled by passing a thermal current between the two heat baths, with no net heat exchange between the heat baths and the electrodes. This effect, termed cooling by transverse heat current, is a mesoscopic heat drag effect. In addition, there is a transverse thermoelectric effect where electrical current and power can be generated by a transverse temperature bias (i.e., the temperature bias between the two heat baths). This transverse thermoelectric effect originates from inelastic-scattering processes and may have advantages for improved figures of merit and power factor due to spatial separation of charge and heat transport. We study the Onsager current-affinity relations, the linear-response transport properties, and the transverse thermoelectric figure of merit of the four-terminal thermoelectric devices for various system parameters. We find that the figures of merit are optimized in different parameter regions for the transverse and the (conventional) longitudinal thermoelectric effects, respectively. Meanwhile, the maximum figure of merit for the transverse thermoelectric effect is higher than the figure of merit for the conventional longitudinal thermoelectric effect. In addition, we investigate the efficiency and power of the cooling by the transverse heat current effect in both linear and nonlinear transport regimes. Finally, we demonstrate that, by exploiting the inelastic transport in the quantum-dot four-terminal systems, a type of Maxwell demon can be realized using nonequilibrium heat baths.

Automated summary

In mesoscopic four-terminal thermoelectric devices, inelastic-scattering processes can lead to unconventional thermoelectric transport, including cooling by transverse heat current and transverse thermoelectric effect. These effects result in improved figures of merit and power factor due to spatial separation of charge and heat transport.