Possible Routes for Efficient Thermo-Electric Energy Conversion in a Molecular Junction

Comparative study between charge and spin thermoelectric figure of merits in an antiferromagnetic ring

Considering the unique and diverse characteristic features of antiferromagnetic (AFM) systems, here in our work, we explore spin-dependent thermoelectric behavior in an AFM ring geometry. A reasonably large (≫1) spin figure of merit, referred to asZST, is obtained under suitable input conditions. Two important prerequisites are (i) breaking the symmetry among up and down spin sub-Hamiltonians and (ii) generating different asymmetric transmission line shapes across a Fermi energy for two opposite spin electrons. Describing the physical system within a tight-binding framework, where spin-dependent scattering occurs due to the interaction of itinerant electrons with local magnetic moments via the usual spin-moment exchange interaction, we compute all the thermoelectric quantities based on Landauer integrals following the Green's function technique. The behavior of charge figure of merit, denoted asZCT, is also discussed along withZST. ThoughZCTreaches above unity, it is much smaller compared toZST. This is the key finding of our investigation. To make the present communication a self-contained one, we compare the results with another arrangement of magnetic moments in a ring-like geometry and in a chain-like one. Our analysis gives a suitable hint that in the presence of spin-dependent scattering, much more favorable energy conversion can be substantiated.

Role of inter-electrode coupling on thermoelectricity in an interferometric geometry: a new proposition

Efficient thermoelectric (TE) energy conversion is one of the most desirable solutions of our current day energy crisis. Exploiting the effect of quantum interference among electronic waves, in this work we propose a prescription of getting high TE efficiency, the so-calledfigure of merit(ZT), considering an interferometric geometry where a loop conductor is clamped between two heat baths. Unlike conventional junction configurations, we introduce an additional path for electron transfer directly from source to drain, due to their close proximity. The interplay between different paths leads to an enhancedZT(ZT > 1). Moreover, the efficiency can be further regulated by tuning the inter-electrode coupling. The effects of magnetic flux threaded by the ring and disorder are also discussed. Our proposed prescription may lead to a new route of designing tunable TE devices at nanoscale level.

Thermal Properties of Ordered and Disordered DNA Chains: Efficient Energy Conversion

Considering the numerous possibilities of having suitable thermoelectric energy conversion at nano-scale level, especially for molecular systems, in the present work we put forward a new proposal along this using a flat DNA segment as a functional element. It is modeled by coupling two chains to a form a two-stranded ladder like geometry, with interactions to first neighbors, within the tight-binding prescription. We critically investigate electrical and thermal properties of DNA molecule depending on the length of the system, temperature, molecule-to-lead coupling and the degree of (correlated) disorder. Our analysis might be helpful in analyzing thermoelectric signatures of correlated and uncorrelated disordered systems, and can be verified in laboratory.