Quantum Mechanics in Quantum Rings
Magnetotransport measurements on a two-terminal semiconductor quantum ring structure are reviewed. The structure has been fabricated by AFM-lithography on a shallow Ga[Al]As heterostructure. In the open regime Aharonov-Bohm oscillations are observed and the phase coherence length can be inferred from their temperature dependence. The ring can also be tuned into the Coulomb blockade regime. It is demonstrated that single-particle level spectra can be reconstructed showing many characteristics of an ideal one-dimensional ring spectrum. Further information about individual quantum states including their position and degree of localisation, their angular momentum and their spin is extracted from measurements in perpendicular and parallel magnetic field and from measurements with asymmetrically applied plunger gate voltages. The ring is an example for a Coulomb blockaded many-electron system in which many aspects of the energy spectrum and the quantum states can be understood quantitatively.
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