"Forbidden" transitions between quantum Hall and insulating phases in p-SiGe heterostructures
Originally posted at http://arxiv.org/abs/cond-mat/0107171v1. Preprint of an article published in Physical Review B, v.64 no.16, 2001.
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 = 1 and 2 and, for the first time, between = 2 and 3 and between = 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 behaviour 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.
M. R. Sakr, Maryam Rahimi, S. V. Kravchenko, P. T. Coleridge, R. L. Williams, and J. Lapointe. ""Forbidden" transitions between quantum Hall and insulating phases in p-SiGe heterostructures" Physics Faculty Publications (2001).
Available at: http://works.bepress.com/skravchenko/2