Observations of quantum interference effects in lateral surface superlattices

In the mesoscopic regime, where the characteristic length of a sample is comparable to the phase coherence length of electrons, quantum interference leading to a magnetoconductance periodic in the magnetic field coupled through a unit cell of a two-dimensional superlattice has been hypothesized for many years. We report here on the observation of such periodic effects in quasi-two-dimensional semiconductor structures with an additional two-dimensional periodic superlattice potential applied. In LSSLs prepared on MODFET material, magnetoconductance measurements made at 4.2K show Aharonov-Bohm type periodic oscillations with h/e periodicity in the flux coupled through each cell of the superlattice. In LSSLs on MESFET material, we find that the conductance is also periodic in the magnetic field, but with replicas of the negative magneto-resistance (signature of weak localization), with separations in magnetic field corresponding to integer changes in the flux per superlattice cell. In addition, the presence of a significant source-drain potential shifts the resonances in magnetic field. These effects are observed for relatively low magnetic fields, B<1 Tesla. Furthermore, conductance fluctuations are observed for samples whose dimensions are large compared to the inelastic mean free path.