Münster 1999 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 39: Symposium: Quanten Hall Systeme

HL 39.8: Fachvortrag

Freitag, 26. März 1999, 13:00–13:30, H1

Electrostatic Imaging of the Two Dimensional Electron Gas in the Quantum Hall Regime — •Amir Yacobi — Department of Condensed Matter Physics
The Weizmann Institute of Science
Rehovot 76100, Israel

Microscopic images of the local electron compressibility, electrostatic potential, and current-induced Hall voltage of a two-dimensional sheet of electrons in the quantum Hall regime are acquired using a single-electron transistor (SET) as a scanned probe. Regions identified as differing in quantum state (Landau level) occupancy of the electrons appear in interrelated ways in all of these properties. The compressibility images show quasi-insulating "incompressible" strips that seperate these regions. The strips follow the contours of constant electron density that match exact occupancy of the Landau levels, and shift accordingly with magnetic field and electron density changes. The surface electrostatic potential distribution has an overall correlation with the compressibility patterns and the density contours marked by them and an abrupt step at the boundaries that provides a direct measure of the energy gap between the Landau levels. In the Hall voltage images we observe a liner Hall voltage drop across the sample away from integer filling suggesting bulk current flow. At integer filling the Hall voltage primarily drops at the boundaries suggesting edge current flow. In the crossover between the two regimes we find substantial structure that correlates strongly with the incompressible patterns.