COULOMB-BLOCKADE OF THE AHARONOV-BOHM EFFECT IN GAAS/ALXGA1-XAS QUANTUM DOTS

We study the effect of Coulomb blockade (CB) on the Aharonov-Bohm (AB) oscillations, observed in the magnetoresistance of small dots in both the quantum Hall and tunneling regimes. In the quantum Hall regime, where one or more edge states pass freely through the dot, the period of oscillation B is well correlated to the dot size, and the temperature-dependent decay of the oscillations is consistent with the expected form of the single-particle magnetospectrum. In the tunneling regime, however, B is enhanced by more than two orders of magnitude over the value expected from the size of the dot, and the resulting oscillations persist to above a degree Kelvin. This behavior can only be explained by considering the effect of CB on the magnetic depopulation of electrons from the isolated dot; these magneto-Coulomb oscillations are the magnetic analogue of the CB oscillations more conventionally observed using electrostatic techniques. These results demonstrate that by varying the coupling of the dot to the source and drain, the resulting AB oscillations can be used to separately probe both the single-particle and CB-related energy scales of small dots. © 1994 The American Physical Society.