High field magneto-transport measurements in GaAs-GaAlAs multilayers

Measurements have been made of magneto-transport in GaAs-Gasub(1-x)Alsub(x)As multi-layers with magnetic fields up to 35 T. At high fields (22 T) a strong, temperature dependent spin splitting of the N = O Landau level is observed. This indicates a strong many-body enhancement of the g factor, since the bare spin splitting (0.7 mV) is much less than the broadening parameter GAMMA (5.3 meV) while the strong temperature dependence below 4.2 K is clear evidence for a temperature dependent enhancement. In the ultra-quantum regime (ν = 2πn/20 approx. <= 1) the magnetoresistance rises very rapidly in contrast to the predictions of independent electron theories and exhibits a weak thermal activation. (orig.)