Regensburg 1998 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 4: Niedrigdimensionale Systeme, Magnetotransport und Quantenhalleffekt

TT 4.6: Hauptvortrag

Montag, 23. März 1998, 16:30–17:00, H 19

Magnetotransport in the extreme quantum limit. — •A.G.M. Jansen — Grenoble High Magnetic Field Laboratory, MPI-FKF and CNRS, B.P. 166X, F-38042 Grenoble, France

Magnetotransport experiments will be presented for metallically doped semiconductors in the extreme quantum limit of the applied magnetic field where only the lowest spin-splitted Landau levels are occupied. Here, both electron-electron interaction and localization effects in a disordered system play a role.

In the extreme quantum limit the effects of electron-electron interaction in disordered systems become so strong that the possible existence of an Hall insulator state has been proposed, i.e. a state with zero dissipative components of the conductivity tensor and non-zero Hall conductivities [1]. Experiments in fields up to 20 T down to 50 mK reveal such a phenomenon in the extrapolation for T → 0.

An oscillatory structure in the Hall coefficient in the field region of spin-splitted Landau levels points to the localization of the minority spin carriers [2]. By combining NMR with magnetotransport, the influence of the hyperfine interaction can be used to separate the influence of spin-splitting from that of the external magnetic field for the anomalous magnetic-field dependence of the Hall effect.

[1] S.S. Murzin, Pis’ma Zh. Eksp. Teor. Fiz. 44, 45 (1986) [JETP Lett. 44, 56 (1986)].

[2] O. Viehweger and K.B. Efetov, Phys. Rev. B 43, 6840 (1991).