NEW RESULTS ON SCALING IN THE INTEGRAL QUANTUM HALL-EFFECT

We report two new results, from temperature dependent transport measurements in two In0.53Ga0.47As/InP heterostructures, concerning the scaling of electronic transport in the integral quantum Hall effect. First, in a sample which has spin resolved Landau levels N=0↓, 1↓, 1↑, we find that the extrema of dρxy dB, d2ρxx dB2 and d3ρ xy dB3 in all spin-split Landau levels diverge like T-α, with a=K, 2K, 3K respectively. The exponent, k=0.42 ± 0.04, uniquely describes the localization to delocalization transition. Moreover, by generalizing these results to higher order derivatives of the transport coefficients ρ, we find that Δρ((B)-ρ(B*)) are invariant under a length scale transformation. Second, in a sample with lower mobility the spin splitting for the N=1 Landau level is not resolved for T>60 mK, we find that both dρxy dB(B*) and 1 ΔB in the N=1 Landau level diverge as T- K 2 for 60 mK < T < 2.5 K. On the other hand, both quantities follow T-K for the spin-split N=0↓ Landau level. © 1990.