Fractional quantum hall effect at low temperatures

We report results of low temperature (65 mK to 770 mK) magneto-transport measurements of the 2 3 quantum Hall plateau in an n-type GaAsAlxGa1-x As heterostructure. Both the diagonal resistivity ρ{variant}xx and the deviation of the Hall resistivity ρ{variant}xy, from the quantized value show thermally activated behavior. The thermal activation energy was measured as a function of the Landau level filling factor, ν, at fixed magnetic fields, B, by varying the density of the two-dimensional electrons with a back-gate bias. The activation energy Δ of ρ{variant}xx is maximum at the center of the Hall plateau, when ν = 2 3, and decreases on either side of it, as ν moves away from 2 3. This resonance-like dependence on ν is characterized by a maximum activation energy, Δm = 830 mK and Δν ν = 8% at B = 92.5 kG. In addition, we have verified that the Hall conductance is quantized to ( 2 3) e² h to an accuracy of 3 parts in 10⁴. The I-V relation is linear down to an electric field of less than 10 ^-5 V cm, indicating that the current carrying state is not pinned. © 1984.

Duke Scholars

Author Albert M. Chang Physics