Short and Long Ranged Impurities in Fractional Quantum Hall Systems

Short and long-range impurities have been examined for fractional quantum Hall systems. There appears to be a consistent computational picture for short range impurities. In the case of long range impurities, calculations agree qualitatively with experiment, in that the critical mobility is very sensitive to long range impurities and the critical mobility for long range impurities is larger than the critical mobility for short range impurities. The physical mechanism of this sensitivity and a quantitative understanding remain a challenging computational issue.