Quantum transport in electron Fabry-Perot interferometers

Abstract

We report experiments on Fabry-Perot electron interferometers in the integer quantum Hall regime. The $\mathrm{Ga}\mathrm{As}∕\mathrm{Al}\mathrm{Ga}\mathrm{As}$ heterostructure devices consist of two constrictions defined by etch trenches in two-dimensional electron layer, enclosing an approximately circular island. The interferometer is formed by counterpropagating chiral edge channels coupled by tunneling in the two constrictions. Interference fringes are observed as conductance oscillations, similar to the Aharonov-Bohm effect. Front gates deposited in etch trenches allow us to fine tune the device and to change the constriction filling $f$ relative to the bulk filling. Quantum-coherent conductance oscillations are observed on the $f=1--4$ plateaus. On plateau $f$, we observe $f$ conductance oscillations per fundamental flux period $h∕e$. This is attributed to the dominance of the electron-electron Coulomb interaction, effectively mixing Landau level occupation. On the other hand, the back-gate charge period is the same (one electron) on all plateaus, independent of filling. This is attributed to the self-consistent electrostatics in the large electron island. We also report dependence of the oscillation period on front-gate voltage for $f=1$, 2, and 4 for three devices. We find a linear dependence, with the slope inversely proportional to $f$ for $f=1$ and 2.