Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 26: Transport im hohen Magnetfeld/Quanten-Hall-Effekt
HL 26.6: Vortrag
Dienstag, 25. März 2003, 16:30–16:45, BEY/154
Composite Fermions Ground State Instabilities at the coincidence of two Landau Levels — •Franco Napoli1,2, Bernhard Kramer1, Nicodemo Magnoli2, Eros Mariani1, Matteo Merlo2, and Maura Sassetti2 — 1I Institut fuer Theoretische Physik, Uni-HH (Germany) — 2Dipartimento di Fisica and INFM, Uni-Genova (Italy)
The effect of interactions near the coincidence of two Landau levels with opposite spins at filling factor 1/2 is investigated. By mapping to Composite Fermions it is shown that the fluctuations of the gauge field induces an effective attractive Fermion interaction. This can lead to a spin-singlet ground state that is separated from the excited states by a gap. The magnitude of the gap is evaluated. The results are consistent with the recently observed half-polarized states in the FQHE at a fixed filling factor. It is suggested that similar anomalies exist for other spin configurations in degenerate spin-up and spin-down Landau levels. An experiment for testing the spin-singlet state is proposed.