Coulomb blockade and the thermopower of a suspended quantum dot

On the basis of the 2D electron gas in an AlGaAs/GaAs membrane separated from a wafer, a one-electron transistor is created that operates on the Coulomb blockade effect—a two-barrier structure with a quantum dot. The separation of the sample from the wafer, which has a large dielectric constant, leads to a sharp decrease in the total capacity C of the quantum dot and, as a result, to high charge energy E _C = e ²/C and critical temperature T _C = E _C/k _B ≈ 40 K. The dependence of the conductance of the quantum dot on the driving and gate voltages includes a rhombic structure characteristic of the Coulomb blockade effect. The phonon-drag thermopower is found in this system. This thermopower exhibits an anomalous alternating dependence on the gate voltage and intensity of the phonon flux. Possible mechanisms are proposed for explaining the indicated anomalies in the thermopower.