Aharonov–Bohm oscillations and equilibrium current distributions in open quantum dot and in ring interferometer

Magnetotransport in two submicron-sized devices formed on the basis of GaAs/AlGaAs structures has been simulated using nonequilibrium Green functions. The effect of a perpendicular magnetic field on quantum transport in a quasi-one-dimensional quantum dot and in an Aharonov–Bohm interferometer has been analyzed in a single-particle approximation. Magnetic field oscillations of two-terminal conductance of the devices, equilibrium (persistent) current distributions and magnetic moment generated in the devices by persistent currents have been determined using numerical methods. Correlations between the magnetic moment, magnetic field oscillations of conductance and energy resonance in a specific magnetic field have been traced. Sufficiently regular conductance oscillations similar to Aharonov–Bohm ones have been revealed for a quasi-one-dimensional quantum dot at small magnetic fields (0.05–0.4 T). For a ring interferometer the contribution to the total equilibrium current and magnetic moment at a specific energy may change abruptly both in magnitude and in sign as a result of changing magnetic field within one Aharonov–Bohm oscillation. We show that the conductance of an interferometer is determined not by the number of modes propagating in the ring but rather by the effect of triangular quantum dots at the ring entrance that produce a strong reflection. The period of the calculated Aharonov–Bohm oscillations is in agreement with the measurement results for these devices.

Aharonov—Bohm oscillations and distributions of equilibrium current in open quantum dot and ring interferometer

Magnetotransport in submicron devices formed on the basis of GaAs/AlGaAs structures is simulated by the method of nonequilibrium Green functions. In the one-particle approximation, the influence of a perpendicular magnetic field on electron transmission through a quasi-one-dimensional quantum dot and the Aharonov—Bohm interferometer is considered. Two-terminal conductance and magnetic moment of the devices are calculated. Two-dimensional patterns of equilibrium (persistent) currents are obtained. The correlations between energy dependences of magnetic moment and conductance are considered. For the quasi-one-dimensional quantum dot, regular conductance oscillations similar to the ABOs were found at low magnetic fields (0.05—0.4 T). In the case of a ring interferometer, the contribution to the total equilibrium current and magnetic moment at a given energy can change sharply both in magnitude and in sign when the magnetic field changes within the same Aharonov—Bohm oscillation. The conductance through the interferometer is determined not by the number of propagating modes, but rather by the influence of triangular quantum dots at the entrances to the ring, causing back scattering. Period of calculated ABOs corresponds to that measured for these devices.