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Mode Spectroscopy and Level Coupling in Ballistic Electron Waveguides

G. Salis, T. Heinzel, K. Ensslin, O. J. Homan, W. Bachtold, K. Maranowski, A. C. Gossard

cond-mat.mes-hallarXiv:cond-mat/9902119

Abstract

A tunable quantum point contact with modes occupied in both transverse directions is studied by magnetotransport experiments. We use conductance quantization of the one-dimensional subbands as a tool to determine the mode spectrum. A magnetic field applied along the direction of the current flow couples the modes. This can be described by an extension of the Darwin-Fock model. Anticrossings are observed as a function of the magnetic field, but not for zero field or perpendicular field directions, indicating coupling of the subbands due to nonparabolicity in the electrical confinement.

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