Regensburg 2000 – scientific programme
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HL: Halbleiterphysik
HL 17: Symposium: Der Quanten-Hall-Effekt wird 20 (II)
HL 17.3: Fachvortrag
Tuesday, March 28, 2000, 16:00–16:30, H15
Correlated phases of two-dimensional electrons in high Landau levels — •M. P. Lilly1, K. B. Cooper1, J. P. Eisenstein1, L. N. Pfeiffer2, and K. W. West2 — 1California Institute of Technology — 2Lucent Technologies, Bell Laboratories
Recent magnetotransport experiments in high mobility two-dimensional electron gases in high Landau levels find evidence for new strongly correlated many-electron states. Near half filling of the third and several higher Landau levels, transport becomes highly anisotropic at temperatures below 100 mK. A resistance maximum forms along one direction, while at the same time a minimum forms in the orthogonal direction. The anisotropy is accompanied by nonlinear transport in the same magnetic field and temperature range. We discuss theoretically proposed charge density wave models, and compare to our results. Further experiments have found that breaking the in-plane symmetry with a parallel magnetic field serves to orient the anisotropy direction. In addition, away from half filling, a re-entrance into the integer quantum Hall effect is observed, indicating the presence of an insulating state. Current-voltage characteristics in this region show an abrupt and hysteretic transition from insulating to conducting properties. This work was supported by the National Science Foundation and the Department of Energy.