  The thermopower of few-electron quantum dots with Kondo correlations is
investigated via a hierarchial equations of motion approach. The thermopower is
determined by the line shape of spectral function within a narrow energy window
defined by temperature. Based on calculations and analyses on single-level and
two-level Anderson impurity models, the underlying relations between
thermopower and various types of electron correlations are elaborated. In
particular, an unconventional sign reversal behavior is predicted for quantum
dots with a suitable inter-level spacing. The new feature highlights the
significance of multi-level effects and their interplay with Kondo
correlations. Our finding and understanding may lead to novel thermoelectric
applications of quantum dots.
