Magnetic field induced metal-insulator transitions in p-SiGe |
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Authors: | P.T Coleridge |
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Affiliation: | Institute for Microstructural Sciences, National Research Council of Canada, Montreal Road, Ottawa, Ont., Canada K1A OR6 |
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Abstract: | Low density modulation doped p-SiGe, where the holes lie in a strained SiGe quantum well, frequently exhibits anomalous insulating behaviour between filling factors ν=2 and 1. There is also anomalous metallic behavior with a metal-insulator transition between the two. It is shown that in these samples exchange effects are sufficiently large to induce the paramagnetic-ferromagnetic phase transition predicted by Giuliani and Quinn in 1985, also that the metallic and insulating behavior is associated with the coincidence of two Landau levels of opposite spin. A model calculation shows that while a ferromagnetic polarization may occur at integer filling factors screening suppresses it for non-integer filling factors. It is argued the Landau levels then stick-together and allow a spin-density instability to form. Because of the strong spin-orbit coupling in p-SiGe the transport properties of this state differ from those of other systems where a similar quantum Hall ferromagnet probably forms. |
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Keywords: | 71.30.+h 73.43.Nq 72.20.&minus i |
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