Sequential and cotunneling behavior in the temperature-dependent thermopower of few-electron quantum dots

We have studied the temperature-dependent thermopower of gate-defined, lateral quantum dots in the Coulomb blockade regime using an electron heating technique. The line shape of the thermopower oscillations depends strongly on the contributing tunneling processes. Between $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and $40\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ a crossover from a pure sawtooth to an intermittent sawtoothlike line shape is observed. The latter is attributed to the increasing dominance of cotunneling processes in the Coulomb blockade regime at low temperatures.