The study of heat-to-work conversion has gained significant attention in recent years, highlighting the potential of nanoscale systems to achieve energy conversion in steady-state devices without any macroscopic moving parts. This review examines the theoretical frameworks governing the steady-state flows of quantum particles like electrons, photons, and phonons within various mesoscopic or nanoscale devices, such as thermoelectric heat engines in the context of quantum dot Aharonov-Bohm (AB) interferometric configurations. Quantum interference effects hold great promise for enhancing the thermoelectric transport properties of such quantum devices by allowing more precise control over energy levels and transport pathways. Driven quantum dot AB networks can maintain quantum coherence and provide precise experimental control. Unlike bulk systems, nanoscale systems like quantum dots reveal distinct quantum interference phenomena, including sharp features in transmission spectra and Fano resonances. This review highlights the distinction between optimization methods that produce boxcar functions and coherent control methods that result in complex interference patterns. It reveals that the effective design of thermoelectric heat engines requires careful tailoring of quantum interference and the magnetic field-induced effects to enhance performance. We emphasize how magnetic fields can change the bounds of power or efficiency. These machines with broken time-reversal symmetry provide insights into directional dependencies and asymmetries in quantum transport. We offer a thorough overview of past and current research on quantum thermoelectric heat engines using the AB effect and present a detailed review of three-terminal AB heat engines, where broken time-reversal symmetry can induce a coherent diode effect. We cover bounds on power and efficiency in systems with broken time-reversal symmetry.

We investigate the thermoelectric performance of a voltage probe and voltage-temperature probe minimally nonlinear irreversible heat engine with broken time-reversal symmetry by considering extended Onsager relations, where a nonlinear power dissipation term ($-\gamma_h{J_L^N}^2$) is added to the heat current. The analytical expressions for efficiency at a given power and efficiency at maximum power, in terms of asymmetry parameters and generalized figures of merit, are derived and analyzed. Our analysis with broken time-reversal symmetry and nonlinear effect reveals two universal bounds on the efficiency at maximum power (EMP) that overshoot the Curzon-Ahlborn (CA) limit. Although the analytical expressions of the bounds on EMP look similar, their respective Carnot efficiency and the asymmetry parameter set the difference between these heat engines which can be proved numerically. We consider a triple-dot Aharonov-Bohm heat engine with a voltage probe and voltage-temperature probe for our numerical simulation experiment. Unlike the voltage probe, the voltage-temperature probe heat engine requires an anisotropy in the system in addition to the magnetic field to break the time-reversal symmetry. In both probe cases, we observe high efficiency with low output power when the tunneling strength $t$ is less than the coupling strength $\gamma$ and vice-versa for $t>\gamma$. Our numerical experiment demonstrates that the efficiency at maximum output power and efficiency at a given power can be enhanced by increasing the power dissipation strength ($\gamma_h$) although the output power remains unaffected. The added nonlinear term helps us to surpass the CA limit of the upper bound on efficiency at maximum power for both cases with and without time-reversal symmetry.

The study of heat-to-work conversion has gained significant attention in recent years, highlighting the potential of nanoscale systems to achieve energy conversion in steady-state devices without any macroscopic moving parts. This review examines the theoretical frameworks governing the steady-state flows of quantum particles like electrons, photons, and phonons within various mesoscopic or nanoscale devices, such as thermoelectric heat engines in the context of quantum dot Aharonov-Bohm (AB) interferometric configurations. Quantum interference effects hold great promise for enhancing the thermoelectric transport properties of such quantum devices by allowing more precise control over energy levels and transport pathways. Driven quantum dot AB networks can maintain quantum coherence and provide precise experimental control. Unlike bulk systems, nanoscale systems like quantum dots reveal distinct quantum interference phenomena, including sharp features in transmission spectra and Fano resonances. This review highlights the distinction between optimization methods that produce boxcar functions and coherent control methods that result in complex interference patterns. It reveals that the effective design of thermoelectric heat engines requires careful tailoring of quantum interference and the magnetic field-induced effects to enhance performance. We emphasize how magnetic fields can change the bounds of power or efficiency. These machines with broken time-reversal symmetry provide insights into directional dependencies and asymmetries in quantum transport. We offer a thorough overview of past and current research on quantum thermoelectric heat engines using the AB effect and present a detailed review of three-terminal AB heat engines, where broken time-reversal symmetry can induce a coherent diode effect. We cover bounds on power and efficiency in systems with broken time-reversal symmetry.