COULOMB-BLOCKADE OSCILLATIONS IN THE THERMOPOWER OF A QUANTUM DOT

The thermopower of a quantum dot, defined in the two-dimensional elect ron gas in a GaAs-AlxGa1-xAs heterostructure, is investigated using a current heating technique. At lattice temperatures k(B)T much smaller than the charging energy e2/C, and at small heating currents, sawtoohl ike thermopower oscillations are observed as a function of gate voltag e, in agreement with a recent theory. In addition, a remarkable sign r eversal of the amplitude of the thermopower oscillations is found in t he non-linear regime at large heating currents.