In the context of designing an efficient thermoelectric energy‐conversion device at nanoscale level, we suggest several important tuning parameters to enhance the performance of thermoelectric converters. We consider a simple molecular junction, which is always helpful to understand the basic mechanisms in a deeper way, where a benzene molecule is coupled to two external baths having unequal temperatures. The key component responsible for achieving better performance is associated with the asymmetric nature of transmission function, and in the present work, we show that it can be implemented in different ways by regulating the physical parameters involving the system. Employing a tight‐binding framework we calculate electrical and thermal conductances, thermopower, and figure of merit (FOM) by using Landauer integrals, and thoroughly examine the critical roles played by molecule‐to‐lead (ML) interface geometry, magnetic field, chemical substituent group, ML coupling, and the direct coupling between the two leads. Our results show that a reasonably large FOM (≫1) can be obtained and lead to a possibility of regulating the efficiency by selectively tuning the physical parameters. We believe that the present analysis will enhance the understanding of designing efficient thermoelectric devices, and can be verified in a laboratory.
We report, for the first time, the phenomenon of thermoelectricity at quantum level, considering a correlated disordered tight-binding one-dimensional lattice where site energies and/or nearest-neighbor hopping integrals are modulated in the cosine form following the well known Aubry–Andre–Harper (AAH) model. The atypical gapped and fragmented energy spectrum yields a transmission function whose steepness is not symmetrical around the Fermi energy, and because of this fact, we obtain a reasonably large figure of merit, a quantity that measures the thermoelectric energy conversion efficiency. The efficiency can be further monitored by means of AAH phase(s) which undoubtedly gives a possible route of designing controlled thermoelectric devices. Evaluating transmission probabilities using the Green’s function formalism, we compute all the thermoelectric quantities based on the Landauer integrals. The diagonal, off-diagonal and generalized versions of the AAH model are taken into account, and in all the cases we find favorable thermoelectric response. At the end of our analysis, we discuss briefly the specific role of phonon thermal conductance on thermoelectric efficiency to make the present investigation a self-contained one. Our theoretical study may shed some light in analyzing thermoelectric phenomena in similar kind of quasicrystals and other related systems.
Figure of merit is an essential quantity to describe the efficiency of a thermoelectric device and asymmetry in transmission probability is the main requirement to increase the efficiency. Keeping this fact in the mind, here we choose a Sierpinski Gasket (SPG) triangle, a nice example of fractal lattice, as the functional element since it has peculiar energy spectrum compared to the traditional elements. In the framework of tight binding (TB) model we calculate all the thermoelectric quantities using Landauer’s prescription. The atypical and strange behavior of transmission function can be further modified by incorporating asymmetry in the hopping integrals of the SPG network. Here, we acquire a remarkably large value of thermoelectric efficiency from the system and we strongly believe that our work can be verified by a suitable experimental setup. The present analysis can easily be generalized in other similar kind of fractal lattices having multiple loops.
A proposal is given to get enhanced thermoelectric performance and its suitable tuning in a quantum wire coupled to a nanoring. The ring is subjected to an in-plane electric field, which is the key controlling parameter of our study. Exploiting the effect of asymmetry in transmission probability and emphasizing the fact that disorderness of the system helps to increase the asymmetric nature, here we suggest two easily adjustable tuning parameters: in-plane electric field and the coupling between the wire and the ring. In the presence of an electric field, the system behaves like an ordered-disordered separated one, which exhibits nontrivial signatures in thermoelectric effects. The wire-ring coupling also plays an important role in regulating the thermoelectric efficiency of the system. We critically investigate all the characteristic features using the Landauer prescription within a tight-binding framework based on Green’s function formalism. We hope that the present analysis may provide some suitable hints for constructing efficient thermoelectric devices at the nanoscale level.
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