New route to enhanced figure of merit at nano scale: effect of Aubry–Andre–Harper modulation

Abstract

Abstract 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.