Thermoelectric response enhanced by surface/edge states in physical nanogaps

Abstract

We propose here a feasible and effective design of new thermoelectric systems based on physical gaps in nanoscale junctions. We show that, depending on the type of features, i.e. the character of surface/edge states, on both sides of the gap, it is possible to achieve rather high figures of merit. In particular, we show that for configurations that have localized states at the surfaces/edges, which translate into sharp resonances in the transmission, it is possible to achieve large Seebeck coefficients and figures of merit by carefully tuning their energy and their coupling to other states. We calculate the thermoelectric coefficients as a function of different parameters and find non-obvious behaviours, like the existence of a certain coupling between the localized and bulk states for which these quantities have a maximum. The highest Seebeck coefficients and figures of merit are achieved for symmetric junctions, which have the same coupling between the localized state and the bulk states on both sides of the gap. The features and trends of the thermoelectric properties and their change with various parameters that we find here cannot only be applied to systems with nanogaps, but also to many other nanoscale junctions, such as e.g. those that have surface states or states localized near the contacts between the nanoscale object and the electrodes. The model presented here can therefore be used to characterize and predict the thermoelectric properties of many different nanoscale junctions and can also serve as a guide for studying other systems. These results pave then the way for the design and fabrication of stable next-generation thermoelectric devices with robust features and improved performances.

arXiv comment16 pages, 9 figures

References in corpus (14)

• The SIESTA method for ab initio order-N materials simulation
• Efficient index handling of multidimensional periodic boundary conditions
• GOLLUM: a next-generation simulation tool for electron, thermal and spin transport
• Room-temperature gating of molecular junctions using few-layer graphene nanogap electrodes
• Giant thermopower and figure of merit in single-molecule devices
• Optimal thermoelectric figure of merit of a molecular junction
• Mechanically Controlled Quantum Interference in Graphene Break Junctions
• Quantum Interference in Graphene Nanoconstrictions
• Acoustic Phonon Tunneling and Heat Transport due to Evanescent Electric Fields
• Impact of Fano and Breit-Wigner resonances in the thermoelectric properties of nanoscale junctions
• Atomistic simulation of phonon heat transport across metallic nanogaps
• First-principles calculations of phonon transport across a vacuum gap
• Spin signatures in the electrical response of graphene nanogaps
• Electronics without bridging components