Thermoelectric signature of the excitation spectrum of a quantum dot

An electon-heating technique has been used to measure the diffusion thermopower of a quantum dot in the Coulomb blockade (CB) regime. When the gate voltage defining the dot is swept, the thermovoltage across the dot oscillates about zero with a period equal to that of the CB oscillations in electrical conductance and with a magnitude consistent with a Landauer formulation. In addition, a reproducible fine structure on top of the CB oscillations in the thermovoltage was observed that appears to result from the N-particle excitation spectrum of the dot.