  We study nonequilibrium thermoelectric transport properties of a correlated
impurity connected to two leads for temperatures below the Kondo scale. At
finite bias, for which a current flows across the leads, we investigate the
differential response of the current to a temperature gradient. In particular,
we compare the influence of a bias voltage and of a finite temperature on this
thermoelectric response. This is of interest from a fundamental point of view
to better understand the two different decoherence mechanisms produced by a
bias voltage and by temperature. Our results show that in this respect the
thermoelectric response behaves differently from the electric conductance. In
particular, while the latter displays a similar qualitative behavior as a
function of voltage and temperature, both in theoretical and experimental
investigations, qualitative differences occur in the case of the thermoelectric
response. In order to understand this effect, we analyze the different
contributions in connection to the behavior of the impurity spectral function
versus temperature. Especially in the regime of strong interactions and large
enough bias voltages we obtain a simple picture based on the asymmetric
suppression or enhancement of the split Kondo peaks as a function of the
temperature gradient. Besides the academic interest, these studies could
additionally provide valuable information to assess the applicability of
quantum dot devices as responsive nanoscale temperature sensors.
