The temperature dependence of the diagonal conductivity, σxx(T), at integer and fractional quantum Hall effect (FQHE) minima was measured in a sample at various densities. We find σxxc, the 1/T→0 extrapolated value of σxx(T) from Arrhenius plots, is different for different densities. While a reasonable (1/q)2 scaling of σxxc at the filling factors ν=p/q is observed at lower densities, the scaling is not seen in the highest density data. We explain this loss of scaling by a breakdown of the assumption for a simple activated formula caused by a crossover between the extended state width, Γ, and T for the measurement. For kT>Γ, the scaling of the 1/T intercept is recovered by plotting σxx(T)×T vs 1/T and fitting to σxx(T)=(σxx*c/T)exp(-ΔE/kT). We attribute the (1/q)2 scaling in σxxc and σxx*c observed at each density to a (1/q)2 scaling in the T=0 conductivity. This supports the assertion of Clark et al. that the charge e* of the quasiparticle excitation from the FQHE ground state at ν=p/q can be determined from σxx(T) and the charge is e*=e/q.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics