Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 18: Quantum Hall Effect
HL 18.3: Talk
Monday, March 14, 2011, 15:00–15:15, POT 151
Probing electron-electron interactions in quantum Hall systems by scanning tunneling spectroscopy — •Marcus Liebmann1, Stefan Becker1, Christoph Karrasch2, Torge Mashoff1, Marco Pratzer1, Volker Meden2, and Markus Morgenstern1 — 1II. Physikalisches Institut B and JARA-FIT, RWTH Aachen University, 52074 Aachen — 2Institut für Theorie der Statistischen Physik and JARA-FIT, RWTH Aachen University, 52074 Aachen
Some of the most intriguing quantum Hall phases, e.g., the fractional quantum Hall phase, are driven by electron-electron (e-e) interaction. A central challenge towards a microscopic investigation of quantum Hall physics dominated by e-e interaction is to provide a sufficiently clean and electrically decoupled system, which can be probed down to the relevant length scales, most notably the magnetic length lB =√ℏ/(eB) ≈ 10 nm (6 T). Using low-temperature scanning tunneling spectroscopy applied to the Cs-induced two dimensional electron system (2DES) on p-type InSb(110), we probe e-e interaction effects in the quantum Hall regime. The 2DES is decoupled from the p-doped bulk of the sample exhibiting spreading resistance within the insulating quantum Hall phases. In quantitative agreement with calculations we find an exchange enhancement of the spin splitting at odd fillings. We observe that both the spatially averaged as well as the local density of states feature a characteristic Coulomb gap at the Fermi level. These results show that e-e interaction effects can be probed down to a resolution below all relevant length scales.