Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 17: Symposium Quantenringe
HL 17.3: Vortrag
Dienstag, 25. März 2003, 12:00–12:30, POT/81
Quantum mechanics in quantum rings — •Thomas Ihn1, Andreas Fuhrer1, Klaus Ensslin1, Werner Wegscheider2, and Max Bichler3 — 1Solid State Physics Laboratory, ETH Hönggerberg, CH-8093 Zürich — 2Inst. f. angew. u. exp. Physik, Univ. Regensburg, 93040 Regensburg — 3Walter Schottky Institut, TU München, Am Coulombwall, 85748 Garching
Interference of particle waves is one of the most fundamental experiments in quantum physics. It can be realised in quantum ring structures fabricated on the basis of two-dimensional electron gases in semiconductor heterostructures. The relative phase of the two transmission amplitudes can be tuned with a magnetic (Aharonov-Bohm, AB) flux piercing the ring. We report conductance measurements of a ring structure performed at 100 mK with variable coupling to source and drain contacts. In the case of weak (tunnelling) coupling we observe Coulomb-blockade in the ring. The extracted single-particle spectrum closely resembles an ideal ring spectrum with 2-3 radial modes and allows to extract the magnitude of the equilibrium persistent currents. Zeeman-splitting of successive ground states of the ring is observed as a function of parallel magnetic field. In the regime of stronger coupling to source and drain we observe the Kondo-effect which is modulated by the AB-flux h/e. Opening the ring strongly to source and drain we observe AB-oscillations at temperatures above 12 K and study the decoherence of the system due to coupling to the environment.