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"Forbidden" transitions between quantum Hall and insulating phases in p-SiGe heterostructures

M. R. Sakr·Maryam Rahimi·S. V. Kravchenko·P. T. Coleridge·R. L. Williams·J. Lapointe
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Abstract

We show that in dilute metallic p-SiGe heterostructures, magnetic field can cause multiple quantum Hall-insulator-quantum Hall transitions. The insulating states are observed between quantum Hall states with filling factors ν=1 and 2 and, for the first time, between ν=2 and 3 and between ν=4 and 6. The latter are in contradiction with the original global phase diagram for the quantum Hall effect. We suggest that the application of a (perpendicular) magnetic field induces insulating behavior in metallic p-SiGe heterostructures in the same way as in Si MOSFETs. This insulator is then in competition with, and interrupted by, integer quantum Hall states leading to the multiple re-entrant transitions. The phase diagram which accounts for these transition is similar to that previously obtained in Si MOSFETs thus confirming its universal character.

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M. R. Sakr, Maryam Rahimi, S. V. Kravchenko, P. T. Coleridge, R. L. Williams, J. Lapointe. 2001-07-09. "Forbidden" transitions between quantum Hall and insulating phases in p-SiGe heterostructures. https://doi.org/10.1103/physrevb.64.161308

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