Electron tunneling spectroscopy of a quantum antidot in the integer quantum Hall regime

Abstract

Quantum antidot, a small potential hill introduced into a two-dimensional electron system, presents an attractive tool to study quantum mechanics of interacting electrons. Here, we present experiments on electron resonant tunneling via a quantum antidot on the integer $i=1$, 2, 3, 4, 5, and 6 quantum Hall plateaus. Several features are reported. First, as a function of magnetic field, we observe up to six quasiperiodic resonant tunneling peaks within the fundamental flux period: When flux $h∕e$ is added to the area of the antidot, there are $i$ peaks on the $i\text{th}$ integer plateau when $i$ spin-polarized Landau levels are occupied. Corresponding backgate voltage data show one peak per added charge $e$ on all integer plateaus. Second, we observe tunneling dips in four-terminal resistance (``forward scattering'') on the even $i=2$, 4, and 6 plateaus when the populations of both spins are nearly equal. We also report an internal structure observed within the $h∕e$ period: On the $i=3$ spin-split plateau, two of the three resonant tunneling peaks are higher and/or closer than the third. Puzzlingly, in this regime, when the backgate voltage is swept, the tunneling peaks are grouped in pairs. These results are attributed to the dominance of the electron-electron Coulomb interaction, effectively mixing the Landau level occupation, and to the self-consistent electrostatics of the antidot.