Comparative study between charge and spin thermoelectric figure of merits in molecular junctions with multiple loops

In this study, we examine the thermoelectric properties of a symmetrically connected naphthalene molecular junction with two Aharonov–Bohm (AB) fluxes. The flux-modulated hopping integrals introduce enhancement in transmission asymmetry and thermoelectric figure of merit. We compare charge- and spin-based thermoelectricity, emphasizing the higher efficiency of spin currents, which avoid heat dissipation. Additionally, we explore the effects of correlated disorder using diagonal and generalized Aubry–André–Harper potentials, revealing their impact on localization transitions and ZT enhancement. The interplay between AB fluxes and disorder offers tunable control over thermoelectric properties, leading to high-efficiency operation. Our results show significant improvements in ZT for both transport types under optimal conditions, providing insights into the design of advanced thermoelectric devices for next-generation energy conversion.