Thermoelectricity of near-resonant tunnel junctions and their relation to Carnot efficiency

We present a conceptual study motivated by electrical and thermoelectrical measurements on various near-resonant tunnel junctions. The squeezable nano junction technique allows the quasi-synchronous measurement of conductance G , I ( V ) characteristics and Seebeck coefficient S . Correlations between G and S are uncovered, in particular boundaries for S ( G ). We find the simplest and consistent description of the observed phenomena in the framework of the single level resonant tunneling model within which measuring I ( V ) and S suffice for determining all model parameters. We can further employ the model for assigning thermoelectric efficiencies η without measuring the heat flow. Within the ensemble of thermoelectric data, junctions with assigned η close to the Carnot limit can be identified. These insights allow providing design rules for optimized thermoelectric efficiency in nanoscale junctions.