Regensburg 2002 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 16: Transport im hohen Magnetfeld / QHE
HL 16.6: Vortrag
Dienstag, 12. März 2002, 12:15–12:30, H15
SET-electrometer as a local potential probe for time resolved measurements on quantum Hall samples — •Torsten Klaffs1, Vladimir Krupenin2, Jürgen Weis3 und Franz Josef Ahlers1 — 1Physikalisch-Technische Bundesanstalt, Bundesalle 100, D-38116 Braunschweig — 2Laboratory of cryoelectronics, Moscow State University, 119889 Moscow — 3Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart
Metal single-electron transistors (SETs) are capable for probing local changes in the potential landscape of a two-dimensional electron gas (2DEG) in a quantum Hall sample. By developing a new 3-angle evaporation technique, we could reduce the size of the SET-island and the tunnel junctions such that SET-operation at temperatures up to T=2 K is possible with a good sensitivity. SETs placed close to the edge of the hall bar give the opportunity to resolve compressible and incompressible edge-states by moving the electrical edge of the 2DEG. On sweeping the magnetic field the SET measures changes in the chemical potential of the 2DEG. While at low magnetic fields the expected sawtooth-like variations in the chemical potential are observed, in small ranges around low integer filling factors the changes are about one magnitude stronger than expected. They change their sign with the sweep-direction of the applied magnetic field. At filling factors with large energy gaps, this effect becomes so strong that the SET detects charge fluctuations (related to relaxation processes) on very long timescales (minutes to hours). The magnitude of this effect rises exponentially with lowering the temperature.