Regensburg 2000 – scientific programme

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HL: Halbleiterphysik

HL 13: Symposium: Der Quanten-Hall-Effekt wird 20 (I)

HL 13.1: Fachvortrag

Tuesday, March 28, 2000, 09:30–10:00, H15

The Quantum-Hall-Effect: After 20 Years Still a Challenge for Theory and Experiment — •G. Landwehr — Physikalisches Institut der Universität Würzburg

That the quantum-Hall-effect (QHE) was of fundamental importance for basic solid state physics became evident immediately after its discovery. However, nobody could foresee that after 2 decades it is still a very active field of research. Although many aspects of the integer QHE are understood, a quantitative theory is still missing. The availability of high mobility GaAs/(GaAl)As heterostructures led to the discovery of the fractional QHE. It can be interpreted by invoking many body effects. Irregularities at occupation number 1/2 remained a mystery for quite some time. However, the composite fermion concept has been successful in explaining many of the findings. In the recent past surprising results were obtained on ultra-high mobility samples for excited Landau states, which are a new challenge for theory. It can be expected, that future exploration of the transport properties of 2D-electron gases in heterostructures ofimproved quality will lead to new insights. Application of other experimental techniques should also deepen our understanding of both the integer and fractional quantum-Hall-effect.