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The Seebeck coefficient, a key parameter describing a material's thermoelectric performance, is generally difficult to measure, and no intrinsic calibration standard exists. Quantum dots and single electron tunneling devices with sharp transmission resonances spaced by many kT have a material-independent Seebeck coefficient that depends only on the electronic charge and the average device temperature T. Here we propose the use of a quantum dot to create an intrinsic, nanoscale standard for the Seebeck coefficient and discuss its implementation.

The Seebeck coefficient S is an important performance characteristic of thermoelectric materials. In this paper we establish the fact that quantum dots and single-electron tunneling devices with narrow, well-spaced energy levels and sharp transmission resonances have a Seebeck coefficient independent of material parameters. By employing a delta function for the transmission resonances we arrive at an intrinsic expression for S in terms of the fundamental electronic charge e. We further confirm the validity of our result in the case of a transmission resonance with finite width.

We present a method for determining a temperature differential across a quantum dot. If the device has a transmission function with sufficiently spaced resonant energies, then one can distinguish electrons which have tunneled from the hot lead, and those which have tunneled from the cold lead. By measuring the thermocurrent as the electrochemical potential is swept through a resonant energy level, information about the transmission function obtained from conductance measurements can be used to deduce the temperature differential of the electron gas across the device.

Nanoscale thermoelectric materials are at the center of current thermoelectric research because they offer higher efficiency than bulk thermoelectrics, which has been attributed to energy selectivity via a strongly modulated electron density of states and lattice thermal conductivity reduction. Our research aims to understand better the efficiency of thermally-induced electron transport using a quantum dot as a model system and to progress toward engineering high-efficiency nanoscale thermoelectric devices for power generation. We discuss here a device used to measure the electronic efficiency of nanoscale thermoelectric processes.

We present a method for the measurement of a temperature differential across a single quantum dot that has transmission resonances that are separated in energy by much more than the thermal energy. We determine numerically that the method is accurate to within a few percent across a wide range of parameters. The proposed method measures the temperature of the electrons that enter the quantum dot and will be useful in experiments that aim to test theory which predicts quantum dots are highly-efficient thermoelectrics., 3 pages, 4 Figures

Quantum dots are model systems for quantum thermoelectric behavior because of their ability to control and measure the effects of electron-energy filtering and quantum confinement on thermoelectric properties. Interestingly, nonlinear thermoelectric properties of such small systems can modify the efficiency of thermoelectric power conversion. Using quantum dots embedded in semiconductor nanowires, we measure thermovoltage and thermocurrent that are strongly nonlinear in the applied thermal bias. We show that most of the observed nonlinear effects can be understood in terms of a renormalization of the quantum-dot energy levels as a function of applied thermal bias and provide a theoretical model of the nonlinear thermovoltage taking renormalization into account. Furthermore, we propose a theory that explains a possible source of the observed, pronounced renormalization effect by the melting of Kondo correlations in the mixed-valence regime. The ability to control nonlinear thermoelectric behavior expands the range in which quantum thermoelectric effects may be used for efficient energy conversion. © IOP Publishing and Deutsche Physikalische Gesellschaft., Financially supported by ONR, ONR Global, the Swedish Energy Agency (grant number 32920–1), the Swedish Research Council (VR), the Thai government, NSF-IGERT, the Knut and Alice Wallenberg Foundation, the MINECO (grant number FIS2011-23526), the Latvian Council of Science (grant number 146/2012), the National Basic Research Program of the Ministry of Science and Technology of China (grant numbers 2012CB932703 and 2012CB932700), the National Natural Science Foundation of China (grant number 91221202) and the Nanometer Structure Consortium at Lund University (nmC@LU).