MINIGAPS AND NOVEL GIANT NEGATIVE MAGNETORESISTANCE IN INAS GASB SEMIMETALLIC SUPERLATTICES/

The magnetoresistance of semimetallic InAs/GaSb superlattices has been measured in parallel magnetic fields. The temperature dependence reve als for the first time the existence of a minigap at the anticrossing points between the electron and hole dispersion relations. At high mag netic fields, samples which are close to intrinsic show surprisingly l arge decreases in resistance of up to 70%. The magnetoresistance also depends on crystal orientation. We present a theoretical model which e xplains the experimental observations and estimates the minigap to be of order 7 meV.