A LOW-TEMPERATURE INSULATING PHASE AT V=1.5 FOR 2D HOLES IN HIGH-MOBILITY SISI1-XGEX HETEROSTRUCTURES WITH LANDAU-LEVEL DEGENERACY

Magneto-transport measurements of the 2D hole system (2DHS) in p-type Si-Si1-xGex heterostructures identify the integer quantum Hall effect (IQHE) at dominantly odd-integer filling factors v and two low-tempera ture insulating phases (IPs) at v = 1.5 and v less than or similar to 0.5, with re-entrance to the quantum Hall effect at v = 1. The tempera ture dependence, current-voltage characteristics, and tilted field and illumination responses of the IP at v = 1.5 indicate that the importa nt physics is associated with an energy degeneracy of adjacent Landau levels of opposite spin, which provides a basis for consideration of a n intrinsic, many-body origin.