Quantum Hall plateau-plateau transition revisited

We observe a temperature-independent point Bc in the longitudinal resistance Rxx of a GaAs-based two-dimensional electron gas in the quantum Hall plateau-plateau transition. This allows us to revisit the spin-degenerate plateau-plateau transition and use the Rxx peak movement with respect to Bc at various temperatures T so as to calculate the critical exponent kappa. We suggest that one measures the maximum of the derivative of Hall resistivity d(rho xy)/dB similar to T-kappa as well as the movement of Rxx at different temperatures, allowing one to measure kappa s using two independent methods. When the peak movement is so large that the resistance peak is no longer in the vicinity of Bc, a largely deviated kappa = 0.54 +/- 0.04 from the value (0.21 +/- 0.02 ) in some spin-degenerate system can be measured.